bert/tokenization_utils_base.py

# coding=utf-8
# Copyright 2020 The HuggingFace Inc. team.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
""" Base classes common to both the slow and the fast tokenization classes:
    PreTrainedTokenizerBase (host all the user fronting encoding methodes)
    Special token mixing (host the special tokens logic) and
    BatchEncoding (wrap the dictionnary of output with special method for the Fast tokenizers)
"""

import copy
import json
import logging
import os
import warnings
from collections import UserDict
from enum import Enum
from typing import Any, Dict, List, NamedTuple, Optional, Sequence, Tuple, Union

import numpy as np
from tokenizers import AddedToken
from tokenizers import Encoding as EncodingFast

from .file_utils import (
    add_end_docstrings,
    cached_path,
    hf_bucket_url,
    is_remote_url,
    is_tf_available,
    is_torch_available,
    torch_required,
)


if is_tf_available():
    import tensorflow as tf
if is_torch_available():
    import torch


logger = logging.getLogger(__name__)

VERY_LARGE_INTEGER = int(1e30)  # This is used to set the max input length for a model with infinite size input
LARGE_INTEGER = int(1e20)  # This is used when we need something big but slightly smaller than VERY_LARGE_INTEGER

# Define type aliases and NamedTuples
TextInput = str
PreTokenizedInput = List[str]
EncodedInput = List[int]
TextInputPair = Tuple[str, str]
PreTokenizedInputPair = Tuple[List[str], List[str]]
EncodedInputPair = Tuple[List[int], List[int]]


# Slow tokenizers used to be saved in three separated files
SPECIAL_TOKENS_MAP_FILE = "special_tokens_map.json"
ADDED_TOKENS_FILE = "added_tokens.json"
TOKENIZER_CONFIG_FILE = "tokenizer_config.json"

# Fast tokenizers (provided by HuggingFace tokenizer's library) can be saved in a single file
FULL_TOKENIZER_FILE = "tokenizer.json"


class ExplicitEnum(Enum):
    """ Enum with more explicit error message for missing values.
    """

    @classmethod
    def _missing_(cls, value):
        raise ValueError(
            "%r is not a valid %s, please select one of %s"
            % (value, cls.__name__, str(list(cls._value2member_map_.keys())))
        )


class TruncationStrategy(ExplicitEnum):
    ONLY_FIRST = "only_first"
    ONLY_SECOND = "only_second"
    LONGEST_FIRST = "longest_first"
    DO_NOT_TRUNCATE = "do_not_truncate"


class PaddingStrategy(ExplicitEnum):
    LONGEST = "longest"
    MAX_LENGTH = "max_length"
    DO_NOT_PAD = "do_not_pad"


class TensorType(ExplicitEnum):
    PYTORCH = "pt"
    TENSORFLOW = "tf"
    NUMPY = "np"


class CharSpan(NamedTuple):
    """ Character span in the original string

        Args:
            start: index of the first character in the original string
            end: index of the character following the last character in the original string
    """

    start: int
    end: int


class TokenSpan(NamedTuple):
    """ Token span in an encoded string (list of tokens)

        Args:
            start: index of the first token in the span
            end: index of the token following the last token in the span
    """

    start: int
    end: int


class BatchEncoding(UserDict):
    """ BatchEncoding hold the output of the encode and batch_encode methods (tokens, attention_masks, etc).
        This class is derived from a python Dictionary and can be used as a dictionnary.
        In addition, this class expose utility methods to map from word/char space to token space.

        Args:
            data (:obj:`dict`): Dictionary of lists/arrays returned by the encode/batch_encode methods ('input_ids', 'attention_mask'...)
            encoding (:obj:`EncodingFast`, :obj:`list(EncodingFast)`, `optional`, defaults to :obj:`None`):
                If the tokenizer is a fast tokenizer which outputs additional informations like mapping from word/char space to token space
                the `EncodingFast` instance or list of instance (for batches) hold these informations.
            tensor_type (:obj:`Union[None, str, TensorType]`, `optional`, defaults to :obj:`None`):
                You can give a tensor_type here to convert the lists of integers in PyTorch/TF/Numpy Tensors at initialization
            prepend_batch_axis (:obj:`bool`, `optional`, defaults to :obj:`False`):
                Set to True to add a batch axis when converting in Tensors (see :obj:`tensor_type` above)
    """

    def __init__(
        self,
        data: Optional[Dict[str, Any]] = None,
        encoding: Optional[Union[EncodingFast, Sequence[EncodingFast]]] = None,
        tensor_type: Union[None, str, TensorType] = None,
        prepend_batch_axis: bool = False,
    ):
        super().__init__(data)

        if isinstance(encoding, EncodingFast):
            encoding = [encoding]

        self._encodings = encoding

        self.convert_to_tensors(tensor_type=tensor_type, prepend_batch_axis=prepend_batch_axis)

    @property
    def is_fast(self):
        """
        Indicate if this BatchEncoding was generated from the result of a PreTrainedTokenizerFast
        Returns: True if generated from subclasses of PreTrainedTokenizerFast, else otherwise
        """
        return self._encodings is not None

    def __getitem__(self, item: Union[int, str]) -> EncodingFast:
        """ If the key is a string, get the value of the dict associated to `key` ('input_ids', 'attention_mask'...)
            If the key is an integer, get the EncodingFast for batch item with index `key`
        """
        if isinstance(item, str):
            return self.data[item]
        elif self._encodings is not None:
            return self._encodings[item]
        else:
            raise KeyError(
                "Indexing with integers (to access backend Encoding for a given batch index) "
                "is not available when using Python based tokenizers"
            )

    def __getattr__(self, item: str):
        try:
            return self.data[item]
        except KeyError:
            raise AttributeError

    def __getstate__(self):
        return {"data": self.data, "encodings": self._encodings}

    def __setstate__(self, state):
        if "data" in state:
            self.data = state["data"]

        if "encodings" in state:
            self._encodings = state["encodings"]

    def keys(self):
        return self.data.keys()

    def values(self):
        return self.data.values()

    def items(self):
        return self.data.items()

    # After this point:
    # Extended properties and methods only available for fast (Rust-based) tokenizers
    # provided by HuggingFace tokenizers library.

    @property
    def encodings(self) -> Optional[List[EncodingFast]]:
        """
        Return the list all encoding from the tokenization process

        Returns: List[EncodingFast] or None if input was tokenized through Python (i.e. not fast) tokenizer
        """
        return self._encodings

    def tokens(self, batch_index: int = 0) -> List[str]:
        if not self._encodings:
            raise ValueError("tokens() is not available when using Python based tokenizers")
        return self._encodings[batch_index].tokens

    def words(self, batch_index: int = 0) -> List[Optional[int]]:
        if not self._encodings:
            raise ValueError("words() is not available when using Python based tokenizers")
        return self._encodings[batch_index].words

    def token_to_word(self, batch_or_token_index: int, token_index: Optional[int] = None) -> int:
        """
        Get the index of the word corresponding (i.e. comprising) to an encoded token
        in a sequence of the batch.

        Can be called as:

        - ``self.token_to_word(token_index)`` if batch size is 1
        - ``self.token_to_word(batch_index, token_index)`` if batch size is greater than 1

        This method is particularly suited when the input sequences are provided as
        pre-tokenized sequences (i.e. words are defined by the user). In this case it allows
        to easily associate encoded tokens with provided tokenized words.

        Args:
            batch_or_token_index (:obj:`int`):
                Index of the sequence in the batch. If the batch only comprise one sequence,
                this can be the index of the token in the sequence
            token_index (:obj:`int`, `optional`):
                If a batch index is provided in `batch_or_token_index`, this can be the index
                of the token in the sequence.

        Returns:
            :obj:`int`:
                index of the word in the input sequence.

        """

        if not self._encodings:
            raise ValueError("token_to_word() is not available when using Python based tokenizers")
        if token_index is not None:
            batch_index = batch_or_token_index
        else:
            batch_index = 0
            token_index = batch_or_token_index
        if batch_index < 0:
            batch_index = self._batch_size + batch_index
        if token_index < 0:
            token_index = self._seq_len + token_index
        return self._encodings[batch_index].token_to_word(token_index)

    def word_to_tokens(self, batch_or_word_index: int, word_index: Optional[int] = None) -> TokenSpan:
        """
        Get the encoded token span corresponding to a word in the sequence of the batch.

        Token spans are returned as a TokenSpan NamedTuple with:

        - start: index of the first token
        - end: index of the token following the last token

        Can be called as:

        - ``self.word_to_tokens(word_index)`` if batch size is 1
        - ``self.word_to_tokens(batch_index, word_index)`` if batch size is greater or equal to 1

        This method is particularly suited when the input sequences are provided as
        pre-tokenized sequences (i.e. words are defined by the user). In this case it allows
        to easily associate encoded tokens with provided tokenized words.

        Args:
            batch_or_word_index (:obj:`int`):
                Index of the sequence in the batch. If the batch only comprises one sequence,
                this can be the index of the word in the sequence
            word_index (:obj:`int`, `optional`):
                If a batch index is provided in `batch_or_token_index`, this can be the index
                of the word in the sequence.

        Returns:
            :obj:`TokenSpan`:
                Span of tokens in the encoded sequence.

                :obj:`TokenSpan` are NamedTuple with:

                - start: index of the first token
                - end: index of the token following the last token
        """

        if not self._encodings:
            raise ValueError("word_to_tokens() is not available when using Python based tokenizers")
        if word_index is not None:
            batch_index = batch_or_word_index
        else:
            batch_index = 0
            word_index = batch_or_word_index
        if batch_index < 0:
            batch_index = self._batch_size + batch_index
        if word_index < 0:
            word_index = self._seq_len + word_index
        return TokenSpan(*(self._encodings[batch_index].word_to_tokens(word_index)))

    def token_to_chars(self, batch_or_token_index: int, token_index: Optional[int] = None) -> CharSpan:
        """
        Get the character span corresponding to an encoded token in a sequence of the batch.

        Character spans are returned as a CharSpan NamedTuple with:

        - start: index of the first character in the original string associated to the token
        - end: index of the character following the last character in the original string associated to the token

        Can be called as:

        - ``self.token_to_chars(token_index)`` if batch size is 1
        - ``self.token_to_chars(batch_index, token_index)`` if batch size is greater or equal to 1

        Args:
            batch_or_token_index (:obj:`int`):
                Index of the sequence in the batch. If the batch only comprise one sequence,
                this can be the index of the token in the sequence
            token_index (:obj:`int`, `optional`):
                If a batch index is provided in `batch_or_token_index`, this can be the index
                of the token or tokens in the sequence.

        Returns:
            :obj:`CharSpan`:
                Span of characters in the original string.

                :obj:`CharSpan` are NamedTuple with:

                - start: index of the first character in the original string
                - end: index of the character following the last character in the original string
        """

        if not self._encodings:
            raise ValueError("token_to_chars() is not available when using Python based tokenizers")
        if token_index is not None:
            batch_index = batch_or_token_index
        else:
            batch_index = 0
            token_index = batch_or_token_index
        return CharSpan(*(self._encodings[batch_index].token_to_chars(token_index)))

    def char_to_token(self, batch_or_char_index: int, char_index: Optional[int] = None) -> int:
        """
        Get the index of the token in the encoded output comprising a character
        in the original string for a sequence of the batch.

        Can be called as:

        - ``self.char_to_token(char_index)`` if batch size is 1
        - ``self.char_to_token(batch_index, char_index)`` if batch size is greater or equal to 1

        This method is particularly suited when the input sequences are provided as
        pre-tokenized sequences (i.e. words are defined by the user). In this case it allows
        to easily associate encoded tokens with provided tokenized words.

        Args:
            batch_or_char_index (:obj:`int`):
                Index of the sequence in the batch. If the batch only comprise one sequence,
                this can be the index of the word in the sequence
            char_index (:obj:`int`, `optional`):
                If a batch index is provided in `batch_or_token_index`, this can be the index
                of the word in the sequence.


        Returns:
            :obj:`int`: Index of the token.
        """

        if not self._encodings:
            raise ValueError("char_to_token() is not available when using Python based tokenizers")
        if char_index is not None:
            batch_index = batch_or_char_index
        else:
            batch_index = 0
            char_index = batch_or_char_index
        return self._encodings[batch_index].char_to_token(char_index)

    def word_to_chars(self, batch_or_word_index: int, word_index: Optional[int] = None) -> CharSpan:
        """
        Get the character span in the original string corresponding to given word in a sequence
        of the batch.

        Character spans are returned as a CharSpan NamedTuple with:

        - start: index of the first character in the original string
        - end: index of the character following the last character in the original string

        Can be called as:

        - ``self.word_to_chars(word_index)`` if batch size is 1
        - ``self.word_to_chars(batch_index, word_index)`` if batch size is greater or equal to 1

        Args:
            batch_or_word_index (:obj:`int`):
                Index of the sequence in the batch. If the batch only comprise one sequence,
                this can be the index of the word in the sequence
            word_index (:obj:`int`, `optional`):
                If a batch index is provided in `batch_or_token_index`, this can be the index
                of the word in the sequence.

        Returns:
            :obj:`CharSpan` or :obj:`List[CharSpan]`:
                Span(s) of the associated character or characters in the string.
                CharSpan are NamedTuple with:

                - start: index of the first character associated to the token in the original string
                - end: index of the character following the last character associated to the token in the original string
        """

        if not self._encodings:
            raise ValueError("word_to_chars() is not available when using Python based tokenizers")
        if word_index is not None:
            batch_index = batch_or_word_index
        else:
            batch_index = 0
            word_index = batch_or_word_index
        return CharSpan(*(self._encodings[batch_index].word_to_chars(word_index)))

    def char_to_word(self, batch_or_char_index: int, char_index: Optional[int] = None) -> int:
        """
        Get the word in the original string corresponding to a character in the original string of
        a sequence of the batch.

        Can be called as:

        - ``self.char_to_word(char_index)`` if batch size is 1
        - ``self.char_to_word(batch_index, char_index)`` if batch size is greater than 1

        This method is particularly suited when the input sequences are provided as
        pre-tokenized sequences (i.e. words are defined by the user). In this case it allows
        to easily associate encoded tokens with provided tokenized words.

        Args:
            batch_or_char_index (:obj:`int`):
                Index of the sequence in the batch. If the batch only comprise one sequence,
                this can be the index of the character in the orginal string.
            char_index (:obj:`int`, `optional`):
                If a batch index is provided in `batch_or_token_index`, this can be the index
                of the character in the orginal string.


        Returns:
            :obj:`int` or :obj:`List[int]`:
                Index or indices of the associated encoded token(s).
        """

        if not self._encodings:
            raise ValueError("char_to_word() is not available when using Python based tokenizers")
        if char_index is not None:
            batch_index = batch_or_char_index
        else:
            batch_index = 0
            char_index = batch_or_char_index
        return self._encodings[batch_index].char_to_word(char_index)

    def convert_to_tensors(self, tensor_type: Union[None, str, TensorType], prepend_batch_axis: bool = False):
        if tensor_type is None:
            return self

        # Convert to TensorType
        if not isinstance(tensor_type, TensorType):
            tensor_type = TensorType(tensor_type)

        # Get a function reference for the correct framework
        if tensor_type == TensorType.TENSORFLOW and is_tf_available():
            as_tensor = tf.constant
        elif tensor_type == TensorType.PYTORCH and is_torch_available():
            as_tensor = torch.tensor
        elif tensor_type == TensorType.NUMPY:
            as_tensor = np.asarray
        else:
            raise ImportError(
                "Unable to convert output to tensors format {}, PyTorch or TensorFlow is not available.".format(
                    tensor_type
                )
            )

        # Do the tensor conversion in batch
        for key, value in self.items():
            try:
                if prepend_batch_axis:
                    value = [value]

                tensor = as_tensor(value)

                # at-least2d
                if tensor.ndim > 2:
                    tensor = tensor.squeeze(0)
                elif tensor.ndim < 2:
                    tensor = tensor[None, :]

                self[key] = tensor
            except:  # noqa E722
                raise ValueError(
                    "Unable to create tensor, you should probably activate truncation and/or padding "
                    "with 'padding=True' 'truncation=True' to have batched tensors with the same length."
                )

        return self

    @torch_required
    def to(self, device: str):
        """Send all values to device by calling v.to(device)"""
        self.data = {k: v.to(device) for k, v in self.data.items()}
        return self


# class AddedToken(UserString):
#     """ AddedToken represents a token to be added to a Tokenizer

#         An AddedToken can have special options defining the way it should behave.

#         Args:
#             content: str:
#                 The content of the token

#             single_word: bool
#                 Whether this token should only match against single word. If True,
#                 this token will never match inside of a word.

#             lstrip: bool
#                 Whether this token should strip all potential whitespaces on the left side.
#                 If True, this token will greedily match any whitespace on the left and then strip
#                 them out.

#             rstrip: bool
#                 Whether this token should strip all potential whitespaces on the right side.
#                 If True, this token will greedily match any whitespace on the right and then strip
#                 them out.
#     """

#     def __init__(
#         self, data: str, single_word: bool = False, lstrip: bool = False, rstrip: bool = False,
#     ):
#         super().__init__(data)

#         self._single_word = single_word
#         self._lstrip = lstrip
#         self._rstrip = rstrip

#     def lower(self):
#         return AddedToken(self.data.lower(), self._single_word, self._lstrip, self._rstrip)


class SpecialTokensMixin:
    """ SpecialTokensMixin is derived by ``PreTrainedTokenizer`` and ``PreTrainedTokenizerFast`` and
        handles specific behaviors related to special tokens. In particular, this class hold the
        attributes which can be used to directly access to these special tokens in a
        model-independant manner and allow to set and update the special tokens.
    """

    SPECIAL_TOKENS_ATTRIBUTES = [
        "bos_token",
        "eos_token",
        "unk_token",
        "sep_token",
        "pad_token",
        "cls_token",
        "mask_token",
        "additional_special_tokens",
    ]

    def __init__(self, verbose=True, **kwargs):
        self._bos_token = None
        self._eos_token = None
        self._unk_token = None
        self._sep_token = None
        self._pad_token = None
        self._cls_token = None
        self._mask_token = None
        self._pad_token_type_id = 0
        self._additional_special_tokens = []
        self.verbose = verbose

        # We directly set the hidden value to allow initialization with special tokens
        # which are not yet in the vocabulary. Necesssary for serialization/de-serialization
        # TODO clean this up at some point (probably by sitching to fast tokenizers)
        for key, value in kwargs.items():
            if key in self.SPECIAL_TOKENS_ATTRIBUTES:
                if key == "additional_special_tokens":
                    assert isinstance(value, (list, tuple)) and all(isinstance(t, str) for t in value)
                    setattr(self, key, value)
                elif isinstance(value, (str, AddedToken)):
                    setattr(self, key, value)
                else:
                    raise TypeError(
                        "special token {} has to be either str or AddedToken but got: {}".format(key, type(value))
                    )

    def sanitize_special_tokens(self) -> int:
        """ Make sure that all the special tokens attributes of the tokenizer (tokenizer.mask_token, tokenizer.cls_token, ...)
            are in the vocabulary. Add the missing ones to the vocabulary if needed.

            Return:
                Number of tokens added in the vocaulary during the operation.
        """
        return self.add_tokens(self.all_special_tokens_extended, special_tokens=True)

    def add_special_tokens(self, special_tokens_dict: Dict[str, Union[str, AddedToken]]) -> int:
        """
        Add a dictionary of special tokens (eos, pad, cls...) to the encoder and link them
        to class attributes. If special tokens are NOT in the vocabulary, they are added
        to it (indexed starting from the last index of the current vocabulary).

        Using `add_special_tokens` will ensure your special tokens can be used in several ways:

        - special tokens are carefully handled by the tokenizer (they are never split)
        - you can easily refer to special tokens using tokenizer class attributes like `tokenizer.cls_token`. This makes it easy to develop model-agnostic training and fine-tuning scripts.

        When possible, special tokens are already registered for provided pretrained models (ex: BertTokenizer cls_token is already registered to be '[CLS]' and XLM's one is also registered to be '</s>')

        Args:
            special_tokens_dict: dict of string. Keys should be in the list of predefined special attributes:
                [``bos_token``, ``eos_token``, ``unk_token``, ``sep_token``, ``pad_token``, ``cls_token``, ``mask_token``,
                ``additional_special_tokens``].

                Tokens are only added if they are not already in the vocabulary (tested by checking if the tokenizer assign the index of the ``unk_token`` to them).

        Returns:
            Number of tokens added to the vocabulary.

        Examples::

            # Let's see how to add a new classification token to GPT-2
            tokenizer = GPT2Tokenizer.from_pretrained('gpt2')
            model = GPT2Model.from_pretrained('gpt2')

            special_tokens_dict = {'cls_token': '<CLS>'}

            num_added_toks = tokenizer.add_special_tokens(special_tokens_dict)
            print('We have added', num_added_toks, 'tokens')
            model.resize_token_embeddings(len(tokenizer))  # Notice: resize_token_embeddings expect to receive the full size of the new vocabulary, i.e. the length of the tokenizer.

            assert tokenizer.cls_token == '<CLS>'
        """
        if not special_tokens_dict:
            return 0

        added_tokens = 0
        for key, value in special_tokens_dict.items():
            assert key in self.SPECIAL_TOKENS_ATTRIBUTES

            if self.verbose:
                logger.info("Assigning %s to the %s key of the tokenizer", value, key)
            setattr(self, key, value)

            if key == "additional_special_tokens":
                assert isinstance(value, (list, tuple)) and all(
                    isinstance(t, (str, AddedToken)) for t in value
                ), f"Tokens {value} for key {key} should all be str or AddedToken instances"
                added_tokens += self.add_tokens(value, special_tokens=True)
            else:
                assert isinstance(
                    value, (str, AddedToken)
                ), f"Token {value} for key {key} should be a str or an AddedToken instance"
                added_tokens += self.add_tokens([value], special_tokens=True)

        return added_tokens

    def add_tokens(self, new_tokens: Union[str, AddedToken, List[str], List[AddedToken]], special_tokens=False) -> int:
        """
        Add a list of new tokens to the tokenizer class. If the new tokens are not in the
        vocabulary, they are added to it with indices starting from length of the current vocabulary.

        Args:
            new_tokens: string or list of string or :class:`~transformers.AddedToken`. Each string is a token to add.
                Tokens are only added if they are not already in the vocabulary. AddedToken wrap a string token to
                let you personnalize it's behavior (Whether this token should only match against single word, whether
                this token should strip all potential whitespaces on the left side, Whether this token should strip
                all potential whitespaces on the right side...).
            special_token: can be used to specify if the token is a special token. This mostly change the normalization
                behavior (special tokens like CLS or [MASK] are usually not lower-cased for instance)

                See details for :class:`~transformers.AddedToken` in HuggingFace tokenizers library.

        Returns:
            Number of tokens added to the vocabulary.

        Examples::

            # Let's see how to increase the vocabulary of Bert model and tokenizer
            tokenizer = BertTokenizerFast.from_pretrained('bert-base-uncased')
            model = BertModel.from_pretrained('bert-base-uncased')

            num_added_toks = tokenizer.add_tokens(['new_tok1', 'my_new-tok2'])
            print('We have added', num_added_toks, 'tokens')
            model.resize_token_embeddings(len(tokenizer))  # Notice: resize_token_embeddings expect to receive the full size of the new vocabulary, i.e. the length of the tokenizer.
        """
        if not new_tokens:
            return 0

        if not isinstance(new_tokens, (list, tuple)):
            new_tokens = [new_tokens]

        return self._add_tokens(new_tokens, special_tokens=special_tokens)

    @property
    def bos_token(self):
        """ Beginning of sentence token (string). Log an error if used while not having been set. """
        if self._bos_token is None and self.verbose:
            logger.error("Using bos_token, but it is not set yet.")
            return None
        return str(self._bos_token)

    @property
    def eos_token(self):
        """ End of sentence token (string). Log an error if used while not having been set. """
        if self._eos_token is None and self.verbose:
            logger.error("Using eos_token, but it is not set yet.")
            return None
        return str(self._eos_token)

    @property
    def unk_token(self):
        """ Unknown token (string). Log an error if used while not having been set. """
        if self._unk_token is None and self.verbose:
            logger.error("Using unk_token, but it is not set yet.")
            return None
        return str(self._unk_token)

    @property
    def sep_token(self):
        """ Separation token (string). E.g. separate context and query in an input sequence. Log an error if used while not having been set. """
        if self._sep_token is None and self.verbose:
            logger.error("Using sep_token, but it is not set yet.")
            return None
        return str(self._sep_token)

    @property
    def pad_token(self):
        """ Padding token (string). Log an error if used while not having been set. """
        if self._pad_token is None and self.verbose:
            logger.error("Using pad_token, but it is not set yet.")
            return None
        return str(self._pad_token)

    @property
    def cls_token(self):
        """ Classification token (string). E.g. to extract a summary of an input sequence leveraging self-attention along the full depth of the model. Log an error if used while not having been set. """
        if self._cls_token is None and self.verbose:
            logger.error("Using cls_token, but it is not set yet.")
            return None
        return str(self._cls_token)

    @property
    def mask_token(self):
        """ Mask token (string). E.g. when training a model with masked-language modeling. Log an error if used while not having been set. """
        if self._mask_token is None and self.verbose:
            logger.error("Using mask_token, but it is not set yet.")
            return None
        return str(self._mask_token)

    @property
    def additional_special_tokens(self):
        """ All the additional special tokens you may want to use (list of strings). Log an error if used while not having been set. """
        if self._additional_special_tokens is None and self.verbose:
            logger.error("Using additional_special_tokens, but it is not set yet.")
            return None
        return [str(tok) for tok in self._additional_special_tokens]

    @bos_token.setter
    def bos_token(self, value):
        self._bos_token = value

    @eos_token.setter
    def eos_token(self, value):
        self._eos_token = value

    @unk_token.setter
    def unk_token(self, value):
        self._unk_token = value

    @sep_token.setter
    def sep_token(self, value):
        self._sep_token = value

    @pad_token.setter
    def pad_token(self, value):
        self._pad_token = value

    @cls_token.setter
    def cls_token(self, value):
        self._cls_token = value

    @mask_token.setter
    def mask_token(self, value):
        self._mask_token = value

    @additional_special_tokens.setter
    def additional_special_tokens(self, value):
        self._additional_special_tokens = value

    @property
    def bos_token_id(self):
        """ Id of the beginning of sentence token in the vocabulary. Log an error if used while not having been set. """
        if self._bos_token is None:
            return None
        return self.convert_tokens_to_ids(self.bos_token)

    @property
    def eos_token_id(self):
        """ Id of the end of sentence token in the vocabulary. Log an error if used while not having been set. """
        if self._eos_token is None:
            return None
        return self.convert_tokens_to_ids(self.eos_token)

    @property
    def unk_token_id(self):
        """ Id of the unknown token in the vocabulary. Log an error if used while not having been set. """
        if self._unk_token is None:
            return None
        return self.convert_tokens_to_ids(self.unk_token)

    @property
    def sep_token_id(self):
        """ Id of the separation token in the vocabulary. E.g. separate context and query in an input sequence. Log an error if used while not having been set. """
        if self._sep_token is None:
            return None
        return self.convert_tokens_to_ids(self.sep_token)

    @property
    def pad_token_id(self):
        """ Id of the padding token in the vocabulary. Log an error if used while not having been set. """
        if self._pad_token is None:
            return None
        return self.convert_tokens_to_ids(self.pad_token)

    @property
    def pad_token_type_id(self):
        """ Id of the padding token type in the vocabulary."""
        return self._pad_token_type_id

    @property
    def cls_token_id(self):
        """ Id of the classification token in the vocabulary. E.g. to extract a summary of an input sequence leveraging self-attention along the full depth of the model. Log an error if used while not having been set. """
        if self._cls_token is None:
            return None
        return self.convert_tokens_to_ids(self.cls_token)

    @property
    def mask_token_id(self):
        """ Id of the mask token in the vocabulary. E.g. when training a model with masked-language modeling. Log an error if used while not having been set. """
        if self._mask_token is None:
            return None
        return self.convert_tokens_to_ids(self.mask_token)

    @property
    def additional_special_tokens_ids(self):
        """ Ids of all the additional special tokens in the vocabulary (list of integers). Log an error if used while not having been set. """
        return self.convert_tokens_to_ids(self.additional_special_tokens)

    @property
    def special_tokens_map(self):
        """ A dictionary mapping special token class attribute (cls_token, unk_token...) to their
            values ('<unk>', '<cls>'...)
            Convert tokens of AddedToken type in string.
            All returned tokens are strings
        """
        set_attr = {}
        for attr in self.SPECIAL_TOKENS_ATTRIBUTES:
            attr_value = getattr(self, "_" + attr)
            if attr_value:
                set_attr[attr] = str(attr_value)
        return set_attr

    @property
    def special_tokens_map_extended(self):
        """ A dictionary mapping special token class attribute (cls_token, unk_token...) to their
            values ('<unk>', '<cls>'...)
            Keep the tokens as AddedToken if they are of this type.

            AddedToken can be used to control more finely how special tokens are tokenized.
        """
        set_attr = {}
        for attr in self.SPECIAL_TOKENS_ATTRIBUTES:
            attr_value = getattr(self, "_" + attr)
            if attr_value:
                set_attr[attr] = attr_value
        return set_attr

    @property
    def all_special_tokens(self):
        """ List all the special tokens ('<unk>', '<cls>'...) mapped to class attributes
            Convert tokens of AddedToken type in string.
            All returned tokens are strings
            (cls_token, unk_token...).
        """
        all_toks = [str(s) for s in self.all_special_tokens_extended]
        return all_toks

    @property
    def all_special_tokens_extended(self):
        """ List all the special tokens ('<unk>', '<cls>'...) mapped to class attributes
            Keep the tokens as AddedToken if they are of this type.

            AddedToken can be used to control more finely how special tokens are tokenized.
        """
        all_toks = []
        set_attr = self.special_tokens_map_extended
        for attr_value in set_attr.values():
            all_toks = all_toks + (list(attr_value) if isinstance(attr_value, (list, tuple)) else [attr_value])
        all_toks = list(set(all_toks))
        return all_toks

    @property
    def all_special_ids(self):
        """ List the vocabulary indices of the special tokens ('<unk>', '<cls>'...) mapped to
            class attributes (cls_token, unk_token...).
        """
        all_toks = self.all_special_tokens
        all_ids = self.convert_tokens_to_ids(all_toks)
        return all_ids


ENCODE_KWARGS_DOCSTRING = r"""
            add_special_tokens (:obj:`bool`, `optional`, defaults to :obj:`True`):
                If set to ``True``, the sequences will be encoded with the special tokens relative
                to their model.
            `padding` (:obj:`Union[bool, str]`, `optional`, defaults to :obj:`False`):
                Activate and control padding. Accepts the following values:

                * `True` or `'longest'`: pad to the longest sequence in the batch (or no padding if only a single sequence if provided),
                * `'max_length'`: pad to a max length specified in `max_length` or to the max acceptable input length for the model if no length is provided (`max_length=None`)
                * `False` or `'do_not_pad'` (default): No padding (i.e. can output batch with sequences of uneven lengths)
            `truncation` (:obj:`Union[bool, str]`, `optional`, defaults to :obj:`False`):
                Activate and control truncation. Accepts the following values:

                * `True` or `'longest_first'`: truncate to a max length specified in `max_length` or to the max acceptable input length for the model if no length is provided (`max_length=None`). This will truncate token by token, removing a token from the longest sequence in the pair if a pair of sequences (or a batch of pairs) is provided,
                * `'only_first'`: truncate to a max length specified in `max_length` or to the max acceptable input length for the model if no length is provided (`max_length=None`). This will only truncate the first sequence of a pair if a pair of sequences (or a batch of pairs) is provided,
                * `'only_second'`: truncate to a max length specified in `max_length` or to the max acceptable input length for the model if no length is provided (`max_length=None`). This will only truncate the second sequence of a pair if a pair of sequences (or a batch of pairs) is provided,
                * `False` or `'do_not_truncate'` (default): No truncation (i.e. can output batch with sequences length greater than the model max admissible input size)
            `max_length` (:obj:`Union[int, None]`, `optional`, defaults to :obj:`None`):
                Control the length for padding/truncation. Accepts the following values

                * `None` (default): This will use the predefined model max length if required by one of the truncation/padding parameters. If the model has no specific max input length (e.g. XLNet) truncation/padding to max length is deactivated.
                * `any integer value` (e.g. `42`): Use this specific maximum length value if required by one of the truncation/padding parameters.
            stride (:obj:`int`, `optional`, defaults to ``0``):
                If set to a number along with max_length, the overflowing tokens returned when `return_overflowing_tokens=True`
                will contain some tokens from the end of the truncated sequence returned to provide some overlap between truncated and overflow ing sequences.
                The value of this argument defines the number of overlapping tokens.
            is_pretokenized (:obj:`bool`, defaults to :obj:`False`):
                Set to True to indicate the input is already tokenized
            pad_to_multiple_of: (optional) Integer if set will pad the sequence to a multiple of the provided value.
                This is especially useful to enable the use of Tensor Core on NVIDIA hardware with compute capability
                >= 7.5 (Volta).
            return_tensors (:obj:`str`, `optional`, defaults to :obj:`None`):
                Can be set to 'tf', 'pt' or 'np' to return respectively TensorFlow :obj:`tf.constant`,
                PyTorch :obj:`torch.Tensor` or Numpy :oj: `np.ndarray` instead of a list of python integers.
"""

ENCODE_PLUS_ADDITIONAL_KWARGS_DOCSTRING = r"""
            return_token_type_ids (:obj:`bool`, `optional`, defaults to :obj:`None`):
                Whether to return token type IDs. If left to the default, will return the token type IDs according
                to the specific tokenizer's default, defined by the :obj:`return_outputs` attribute.

                `What are token type IDs? <../glossary.html#token-type-ids>`_
            return_attention_mask (:obj:`bool`, `optional`, defaults to :obj:`none`):
                Whether to return the attention mask. If left to the default, will return the attention mask according
                to the specific tokenizer's default, defined by the :obj:`return_outputs` attribute.

                `What are attention masks? <../glossary.html#attention-mask>`__
            return_overflowing_tokens (:obj:`bool`, `optional`, defaults to :obj:`False`):
                Set to True to return overflowing token sequences (default False).
            return_special_tokens_mask (:obj:`bool`, `optional`, defaults to :obj:`False`):
                Set to True to return special tokens mask information (default False).
            return_offsets_mapping (:obj:`bool`, `optional`, defaults to :obj:`False`):
                Set to True to return (char_start, char_end) for each token (default False).
                If using Python's tokenizer, this method will raise NotImplementedError.
                This one is only available on fast tokenizers inheriting from PreTrainedTokenizerFast.
            **kwargs: passed to the `self.tokenize()` method

        Return:
            A Dictionary of shape::

                {
                    input_ids: list[int],
                    token_type_ids: list[int] if return_token_type_ids is True (default)
                    attention_mask: list[int] if return_attention_mask is True (default)
                    overflowing_tokens: list[int] if the tokenizer is a slow tokenize, else a List[List[int]] if a ``max_length`` is specified and ``return_overflowing_tokens=True``
                    special_tokens_mask: list[int] if ``add_special_tokens`` if set to ``True``
                    and return_special_tokens_mask is True
                }

            With the fields:

            - ``input_ids``: list of token ids to be fed to a model
            - ``token_type_ids``: list of token type ids to be fed to a model
            - ``attention_mask``: list of indices specifying which tokens should be attended to by the model
            - ``overflowing_tokens``: list of overflowing tokens sequences if a max length is specified and ``return_overflowing_tokens=True``.
            - ``special_tokens_mask``: if adding special tokens, this is a list of [0, 1], with 0 specifying special added
              tokens and 1 specifying sequence tokens.
"""


class PreTrainedTokenizerBase(SpecialTokensMixin):
    """ Base class for slow and fast tokenizers.

        Handle shared (mostly boiler plate) methods for slow and fast tokenizers.
    """

    vocab_files_names: Dict[str, str] = {}
    pretrained_vocab_files_map: Dict[str, Dict[str, str]] = {}
    pretrained_init_configuration: Dict[str, Dict[str, Any]] = {}
    max_model_input_sizes: Dict[str, int] = {}
    model_input_names: List[str] = ["token_type_ids", "attention_mask"]

    padding_side: str = "right"

    def __init__(self, **kwargs):
        # inputs and kwargs for saving and re-loading (see ``from_pretrained`` and ``save_pretrained``)
        self.init_inputs = ()
        self.init_kwargs = kwargs

        # For backward compatibility we fallback to set model_max_length from max_len if provided
        model_max_length = kwargs.pop("model_max_length", kwargs.pop("max_len", None))
        self.model_max_length = model_max_length if model_max_length is not None else VERY_LARGE_INTEGER

        # Padding side is right by default and overridden in subclasses. If specified in the kwargs, it is changed.
        self.padding_side = kwargs.pop("padding_side", self.padding_side)
        assert self.padding_side in [
            "right",
            "left",
        ], f"Padding side should be selected between 'right' and 'left', current value: {self.padding_side}"
        self.model_input_names = kwargs.pop("model_input_names", self.model_input_names)

        super().__init__(**kwargs)

    @property
    def max_len(self) -> int:
        """ Kept here for backward compatibility.
            Now renamed to `model_max_length` to avoid ambiguity.
        """
        return self.model_max_length

    @property
    def max_len_single_sentence(self) -> int:
        return self.model_max_length - self.num_special_tokens_to_add(pair=False)

    @property
    def max_len_sentences_pair(self) -> int:
        return self.model_max_length - self.num_special_tokens_to_add(pair=True)

    @max_len_single_sentence.setter
    def max_len_single_sentence(self, value) -> int:
        """ For backward compatibility, allow to try to setup 'max_len_single_sentence' """
        if value == self.model_max_length - self.num_special_tokens_to_add(pair=False) and self.verbose:
            logger.warning(
                "Setting 'max_len_single_sentence' is now deprecated. " "This value is automatically set up."
            )
        else:
            raise ValueError(
                "Setting 'max_len_single_sentence' is now deprecated. " "This value is automatically set up."
            )

    @max_len_sentences_pair.setter
    def max_len_sentences_pair(self, value) -> int:
        """ For backward compatibility, allow to try to setup 'max_len_sentences_pair' """
        if value == self.model_max_length - self.num_special_tokens_to_add(pair=True) and self.verbose:
            logger.warning(
                "Setting 'max_len_sentences_pair' is now deprecated. " "This value is automatically set up."
            )
        else:
            raise ValueError(
                "Setting 'max_len_sentences_pair' is now deprecated. " "This value is automatically set up."
            )

    @classmethod
    def from_pretrained(cls, *inputs, **kwargs):
        r"""
        Instantiate a :class:`~transformers.PreTrainedTokenizer` (or a derived class) from a predefined tokenizer.

        Args:
            pretrained_model_name_or_path: either:

                - a string with the `shortcut name` of a predefined tokenizer to load from cache or download, e.g.: ``bert-base-uncased``.
                - a string with the `identifier name` of a predefined tokenizer that was user-uploaded to our S3, e.g.: ``dbmdz/bert-base-german-cased``.
                - a path to a `directory` containing vocabulary files required by the tokenizer, for instance saved using the :func:`~transformers.PreTrainedTokenizer.save_pretrained` method, e.g.: ``./my_model_directory/``.
                - (not applicable to all derived classes, deprecated) a path or url to a single saved vocabulary file if and only if the tokenizer only requires a single vocabulary file (e.g. Bert, XLNet), e.g.: ``./my_model_directory/vocab.txt``.

            cache_dir: (`optional`) string:
                Path to a directory in which a downloaded predefined tokenizer vocabulary files should be cached if the standard cache should not be used.

            force_download: (`optional`) boolean, default False:
                Force to (re-)download the vocabulary files and override the cached versions if they exists.

            resume_download: (`optional`) boolean, default False:
                Do not delete incompletely recieved file. Attempt to resume the download if such a file exists.

            proxies: (`optional`) dict, default None:
                A dictionary of proxy servers to use by protocol or endpoint, e.g.: {'http': 'foo.bar:3128', 'http://hostname': 'foo.bar:4012'}.
                The proxies are used on each request.

            inputs: (`optional`) positional arguments: will be passed to the Tokenizer ``__init__`` method.

            kwargs: (`optional`) keyword arguments: will be passed to the Tokenizer ``__init__`` method. Can be used to set special tokens like ``bos_token``, ``eos_token``, ``unk_token``, ``sep_token``, ``pad_token``, ``cls_token``, ``mask_token``, ``additional_special_tokens``. See parameters in the doc string of :class:`~transformers.PreTrainedTokenizer` for details.

        Examples::

            # We can't instantiate directly the base class `PreTrainedTokenizer` so let's show our examples on a derived class: BertTokenizer

            # Download vocabulary from S3 and cache.
            tokenizer = BertTokenizer.from_pretrained('bert-base-uncased')

            # Download vocabulary from S3 (user-uploaded) and cache.
            tokenizer = BertTokenizer.from_pretrained('dbmdz/bert-base-german-cased')

            # If vocabulary files are in a directory (e.g. tokenizer was saved using `save_pretrained('./test/saved_model/')`)
            tokenizer = BertTokenizer.from_pretrained('./test/saved_model/')

            # If the tokenizer uses a single vocabulary file, you can point directly to this file
            tokenizer = BertTokenizer.from_pretrained('./test/saved_model/my_vocab.txt')

            # You can link tokens to special vocabulary when instantiating
            tokenizer = BertTokenizer.from_pretrained('bert-base-uncased', unk_token='<unk>')
            # You should be sure '<unk>' is in the vocabulary when doing that.
            # Otherwise use tokenizer.add_special_tokens({'unk_token': '<unk>'}) instead)
            assert tokenizer.unk_token == '<unk>'

        """
        return cls._from_pretrained(*inputs, **kwargs)

    @classmethod
    def _from_pretrained(cls, pretrained_model_name_or_path, *init_inputs, **kwargs):
        cache_dir = kwargs.pop("cache_dir", None)
        force_download = kwargs.pop("force_download", False)
        resume_download = kwargs.pop("resume_download", False)
        proxies = kwargs.pop("proxies", None)
        local_files_only = kwargs.pop("local_files_only", False)

        s3_models = list(cls.max_model_input_sizes.keys())
        vocab_files = {}
        init_configuration = {}
        if pretrained_model_name_or_path in s3_models:
            # Get the vocabulary from AWS S3 bucket
            for file_id, map_list in cls.pretrained_vocab_files_map.items():
                vocab_files[file_id] = map_list[pretrained_model_name_or_path]
            if (
                cls.pretrained_init_configuration
                and pretrained_model_name_or_path in cls.pretrained_init_configuration
            ):
                init_configuration = cls.pretrained_init_configuration[pretrained_model_name_or_path].copy()
        else:
            # Get the vocabulary from local files
            logger.info(
                "Model name '{}' not found in model shortcut name list ({}). "
                "Assuming '{}' is a path, a model identifier, or url to a directory containing tokenizer files.".format(
                    pretrained_model_name_or_path, ", ".join(s3_models), pretrained_model_name_or_path
                )
            )

            if os.path.isfile(pretrained_model_name_or_path) or is_remote_url(pretrained_model_name_or_path):
                if len(cls.vocab_files_names) > 1:
                    raise ValueError(
                        "Calling {}.from_pretrained() with the path to a single file or url is not supported."
                        "Use a model identifier or the path to a directory instead.".format(cls.__name__)
                    )
                logger.warning(
                    "Calling {}.from_pretrained() with the path to a single file or url is deprecated".format(
                        cls.__name__
                    )
                )
                file_id = list(cls.vocab_files_names.keys())[0]
                vocab_files[file_id] = pretrained_model_name_or_path
            else:
                # At this point pretrained_model_name_or_path is either a directory or a model identifier name
                additional_files_names = {
                    "added_tokens_file": ADDED_TOKENS_FILE,
                    "special_tokens_map_file": SPECIAL_TOKENS_MAP_FILE,
                    "tokenizer_config_file": TOKENIZER_CONFIG_FILE,
                    "full_tokenizer_file": FULL_TOKENIZER_FILE,
                }
                # Look for the tokenizer files
                for file_id, file_name in {**cls.vocab_files_names, **additional_files_names}.items():
                    if os.path.isdir(pretrained_model_name_or_path):
                        full_file_name = os.path.join(pretrained_model_name_or_path, file_name)
                        if not os.path.exists(full_file_name):
                            logger.info("Didn't find file {}. We won't load it.".format(full_file_name))
                            full_file_name = None
                    else:
                        full_file_name = hf_bucket_url(
                            pretrained_model_name_or_path, filename=file_name, use_cdn=False
                        )

                    vocab_files[file_id] = full_file_name

        # Get files from url, cache, or disk depending on the case
        try:
            resolved_vocab_files = {}
            for file_id, file_path in vocab_files.items():
                if file_path is None:
                    resolved_vocab_files[file_id] = None
                else:
                    resolved_vocab_files[file_id] = cached_path(
                        file_path,
                        cache_dir=cache_dir,
                        force_download=force_download,
                        proxies=proxies,
                        resume_download=resume_download,
                        local_files_only=local_files_only,
                    )
        except EnvironmentError:
            if pretrained_model_name_or_path in s3_models:
                msg = "Couldn't reach server at '{}' to download vocabulary files."
            else:
                msg = (
                    "Model name '{}' was not found in tokenizers model name list ({}). "
                    "We assumed '{}' was a path or url to a directory containing vocabulary files "
                    "named {}, but couldn't find such vocabulary files at this path or url.".format(
                        pretrained_model_name_or_path,
                        ", ".join(s3_models),
                        pretrained_model_name_or_path,
                        list(cls.vocab_files_names.values()),
                    )
                )

            raise EnvironmentError(msg)

        if all(full_file_name is None for full_file_name in resolved_vocab_files.values()):
            raise EnvironmentError(
                "Model name '{}' was not found in tokenizers model name list ({}). "
                "We assumed '{}' was a path, a model identifier, or url to a directory containing vocabulary files "
                "named {} but couldn't find such vocabulary files at this path or url.".format(
                    pretrained_model_name_or_path,
                    ", ".join(s3_models),
                    pretrained_model_name_or_path,
                    list(cls.vocab_files_names.values()),
                )
            )

        for file_id, file_path in vocab_files.items():
            if file_path == resolved_vocab_files[file_id]:
                logger.info("loading file {}".format(file_path))
            else:
                logger.info("loading file {} from cache at {}".format(file_path, resolved_vocab_files[file_id]))

        # Prepare tokenizer initialization kwargs
        # Did we saved some inputs and kwargs to reload ?
        tokenizer_config_file = resolved_vocab_files.pop("tokenizer_config_file", None)
        if tokenizer_config_file is not None:
            with open(tokenizer_config_file, encoding="utf-8") as tokenizer_config_handle:
                init_kwargs = json.load(tokenizer_config_handle)
            saved_init_inputs = init_kwargs.pop("init_inputs", ())
            if not init_inputs:
                init_inputs = saved_init_inputs
        else:
            init_kwargs = init_configuration

        # Update with newly provided kwargs
        init_kwargs.update(kwargs)

        # Set max length if needed
        if pretrained_model_name_or_path in cls.max_model_input_sizes:
            # if we're using a pretrained model, ensure the tokenizer
            # wont index sequences longer than the number of positional embeddings
            model_max_length = cls.max_model_input_sizes[pretrained_model_name_or_path]
            if model_max_length is not None and isinstance(model_max_length, (int, float)):
                init_kwargs["model_max_length"] = min(init_kwargs.get("model_max_length", int(1e30)), model_max_length)

        # Merge resolved_vocab_files arguments in init_kwargs.
        added_tokens_file = resolved_vocab_files.pop("added_tokens_file", None)
        for args_name, file_path in resolved_vocab_files.items():
            if args_name not in init_kwargs:
                init_kwargs[args_name] = file_path

        # Instantiate tokenizer.
        try:
            tokenizer = cls(*init_inputs, **init_kwargs)
        except OSError:
            raise OSError(
                "Unable to load vocabulary from file. "
                "Please check that the provided vocabulary is accessible and not corrupted."
            )

        # Save inputs and kwargs for saving and re-loading with ``save_pretrained``
        tokenizer.init_inputs = init_inputs
        tokenizer.init_kwargs = init_kwargs

        # If there is a complementary special token map, load it
        special_tokens_map_file = resolved_vocab_files.pop("special_tokens_map_file", None)
        if special_tokens_map_file is not None:
            with open(special_tokens_map_file, encoding="utf-8") as special_tokens_map_handle:
                special_tokens_map = json.load(special_tokens_map_handle)

            for key, value in special_tokens_map.items():
                if isinstance(value, dict):
                    value = AddedToken(**value)
                setattr(tokenizer, key, value)

        # Add supplementary tokens.
        special_tokens = tokenizer.all_special_tokens
        if added_tokens_file is not None:
            with open(added_tokens_file, encoding="utf-8") as added_tokens_handle:
                added_tok_encoder = json.load(added_tokens_handle)

            # Sort added tokens by index
            added_tok_encoder_sorted = list(sorted(added_tok_encoder.items(), key=lambda x: x[1]))

            for token, index in added_tok_encoder_sorted:
                assert index == len(tokenizer), (
                    f"Non-consecutive added token '{token}' found. "
                    f"Should have index {len(tokenizer)} but has index {index} in saved vocabulary."
                )
                tokenizer.add_tokens(token, special_tokens=bool(token in special_tokens))

        # Check all our special tokens are registrered as "no split" token (we don't cut them) and are in the vocab
        added_tokens = tokenizer.sanitize_special_tokens()
        if added_tokens:
            logger.warning(
                "Special tokens have been added in the vocabulary, make sure the associated word emebedding are fine-tuned or trained."
            )

        return tokenizer

    def save_pretrained(self, save_directory) -> Tuple[str]:
        """ Save the tokenizer vocabulary files together with:
                - added tokens,
                - special-tokens-to-class-attributes-mapping,
                - tokenizer instantiation positional and keywords inputs (e.g. do_lower_case for Bert).

            Warning: This won't save modifications you may have applied to the tokenizer after the instantiation
            (e.g. modifying tokenizer.do_lower_case after creation).

            This method make sure the full tokenizer can then be re-loaded using the
            :func:`~transformers.PreTrainedTokenizer.from_pretrained` class method.
        """
        if os.path.isfile(save_directory):
            logger.error("Provided path ({}) should be a directory, not a file".format(save_directory))
            return
        os.makedirs(save_directory, exist_ok=True)

        special_tokens_map_file = os.path.join(save_directory, SPECIAL_TOKENS_MAP_FILE)
        added_tokens_file = os.path.join(save_directory, ADDED_TOKENS_FILE)
        tokenizer_config_file = os.path.join(save_directory, TOKENIZER_CONFIG_FILE)

        tokenizer_config = copy.deepcopy(self.init_kwargs)
        if len(self.init_inputs) > 0:
            tokenizer_config["init_inputs"] = copy.deepcopy(self.init_inputs)
        for file_id in self.vocab_files_names.keys():
            tokenizer_config.pop(file_id, None)

        with open(tokenizer_config_file, "w", encoding="utf-8") as f:
            f.write(json.dumps(tokenizer_config, ensure_ascii=False))

        with open(special_tokens_map_file, "w", encoding="utf-8") as f:
            write_dict = {}
            for key, value in self.special_tokens_map_extended.items():
                if isinstance(value, AddedToken):
                    write_dict[key] = value.__getstate__()
                else:
                    write_dict[key] = value
            f.write(json.dumps(write_dict, ensure_ascii=False))

        added_vocab = self.get_added_vocab()
        if added_vocab:
            with open(added_tokens_file, "w", encoding="utf-8") as f:
                out_str = json.dumps(added_vocab, ensure_ascii=False)
                f.write(out_str)

        vocab_files = self.save_vocabulary(save_directory)

        return vocab_files + (special_tokens_map_file, added_tokens_file)

    @add_end_docstrings(
        ENCODE_KWARGS_DOCSTRING,
        """
            **kwargs: passed to the `self.tokenize()` method.
    """,
    )
    def encode(
        self,
        text: Union[TextInput, PreTokenizedInput, EncodedInput],
        text_pair: Optional[Union[TextInput, PreTokenizedInput, EncodedInput]] = None,
        add_special_tokens: bool = True,
        padding: Union[bool, str] = False,
        truncation: Union[bool, str] = False,
        max_length: Optional[int] = None,
        stride: int = 0,
        return_tensors: Optional[Union[str, TensorType]] = None,
        **kwargs
    ):
        """
        Converts a string in a sequence of ids (integer), using the tokenizer and vocabulary.

        Same as doing ``self.convert_tokens_to_ids(self.tokenize(text))``.

        Args:
            text (:obj:`str`, :obj:`List[str]` or :obj:`List[int]`):
                The first sequence to be encoded. This can be a string, a list of strings (tokenized string using
                the `tokenize` method) or a list of integers (tokenized string ids using the `convert_tokens_to_ids`
                method)
            text_pair (:obj:`str`, :obj:`List[str]` or :obj:`List[int]`, `optional`, defaults to :obj:`None`):
                Optional second sequence to be encoded. This can be a string, a list of strings (tokenized
                string using the `tokenize` method) or a list of integers (tokenized string ids using the
                `convert_tokens_to_ids` method)
        """
        encoded_inputs = self.encode_plus(
            text,
            text_pair=text_pair,
            add_special_tokens=add_special_tokens,
            padding=padding,
            truncation=truncation,
            max_length=max_length,
            stride=stride,
            return_tensors=return_tensors,
            **kwargs,
        )

        return encoded_inputs["input_ids"]

    def num_special_tokens_to_add(self, pair: bool = False) -> int:
        raise NotImplementedError

    def _get_padding_truncation_strategies(
        self, padding=False, truncation=False, max_length=None, pad_to_multiple_of=None, verbose=True, **kwargs
    ):
        """ Find the correct padding/truncation strategy with backward compatibility
            for old arguments (truncation_strategy and pad_to_max_length) and behaviors.
        """
        old_truncation_strategy = kwargs.pop("truncation_strategy", "do_not_truncate")
        old_pad_to_max_length = kwargs.pop("pad_to_max_length", False)

        # Backward compatibility for previous behavior, maybe we should deprecate it:
        # If you only set max_length, it activates truncation for max_length
        if max_length is not None and padding is False and truncation is False:
            if verbose:
                logger.warning(
                    "Truncation was not explicitely activated but `max_length` is provided a specific value, "
                    "please use `truncation=True` to explicitely truncate examples to max length. "
                    "Defaulting to 'longest_first' truncation strategy. "
                    "If you encode pairs of sequences (GLUE-style) with the tokenizer you can select this strategy "
                    "more precisely by providing a specific strategy to `truncation`."
                )
            truncation = "longest_first"

        # Get padding strategy
        if padding is False and old_pad_to_max_length:
            if verbose:
                warnings.warn(
                    "The `pad_to_max_length` argument is deprecated and will be removed in a future version, "
                    "use `padding=True` or `padding='longest'` to pad to the longest sequence in the batch, or "
                    "use `padding='max_length'` to pad to a max length. In this case, you can give a specific "
                    "length with `max_length` (e.g. `max_length=45`) or leave max_length to None to pad to the "
                    "maximal input size of the model (e.g. 512 for Bert).",
                    DeprecationWarning,
                )
            if max_length is None:
                padding_strategy = PaddingStrategy.LONGEST
            else:
                padding_strategy = PaddingStrategy.MAX_LENGTH
        elif padding is not False:
            if padding is True:
                padding_strategy = PaddingStrategy.LONGEST  # Default to pad to the longest sequence in the batch
            elif not isinstance(padding, PaddingStrategy):
                padding_strategy = PaddingStrategy(padding)
        else:
            padding_strategy = PaddingStrategy.DO_NOT_PAD

        # Get truncation strategy
        if truncation is False and old_truncation_strategy != "do_not_truncate":
            if verbose:
                warnings.warn(
                    "The `truncation_strategy` argument is deprecated and will be removed in a future version, "
                    "use `truncation=True` to truncate examples to a max length. You can give a specific "
                    "length with `max_length` (e.g. `max_length=45`) or leave max_length to None to truncate to the "
                    "maximal input size of the model (e.g. 512 for Bert). "
                    " If you have pairs of inputs, you can give a specific truncation strategy selected among "
                    "`truncation='only_first'` (will only truncate the first sentence in the pairs) "
                    "`truncation='only_second'` (will only truncate the second sentence in the pairs) "
                    "or `truncation='longest_first'` (will iteratively remove tokens from the longest sentence in the pairs).",
                    DeprecationWarning,
                )
            truncation_strategy = TruncationStrategy(old_truncation_strategy)
        elif truncation is not False:
            if truncation is True:
                truncation_strategy = (
                    TruncationStrategy.LONGEST_FIRST
                )  # Default to truncate the longest sequences in pairs of inputs
            elif not isinstance(truncation, TruncationStrategy):
                truncation_strategy = TruncationStrategy(truncation)
        else:
            truncation_strategy = TruncationStrategy.DO_NOT_TRUNCATE

        # Set max length if needed
        if max_length is None:
            if padding_strategy == PaddingStrategy.MAX_LENGTH:
                if self.model_max_length > LARGE_INTEGER:
                    if verbose:
                        logger.warning(
                            "Asking to pad to max_length but no maximum length is provided and the model has no predefined maximum length. "
                            "Default to no padding."
                        )
                    padding_strategy = PaddingStrategy.DO_NOT_PAD
                else:
                    max_length = self.model_max_length

            if truncation_strategy != TruncationStrategy.DO_NOT_TRUNCATE:
                if self.model_max_length > LARGE_INTEGER:
                    if verbose:
                        logger.warning(
                            "Asking to truncate to max_length but no maximum length is provided and the model has no predefined maximum length. "
                            "Default to no truncation."
                        )
                    truncation_strategy = TruncationStrategy.DO_NOT_TRUNCATE
                else:
                    max_length = self.model_max_length

        # Test if we have a padding token
        if padding_strategy != PaddingStrategy.DO_NOT_PAD and (not self.pad_token or self.pad_token_id < 0):
            raise ValueError(
                "Asking to pad but the tokenizer does not have a padding token. "
                "Please select a token to use as `pad_token` `(tokenizer.pad_token = tokenizer.eos_token e.g.)` "
                "or add a new pad token via `tokenizer.add_special_tokens({'pad_token': '[PAD]'})`."
            )

        # Check that we will truncate to a multiple of pad_to_multiple_of if both are provided
        if (
            truncation_strategy != TruncationStrategy.DO_NOT_TRUNCATE
            and padding_strategy != PaddingStrategy.DO_NOT_PAD
            and pad_to_multiple_of is not None
            and max_length is not None
            and (max_length % pad_to_multiple_of != 0)
        ):
            raise ValueError(
                f"Truncation and padding are both activated but "
                f"truncation length ({max_length}) is not a multiple of pad_to_multiple_of ({pad_to_multiple_of})."
            )

        return padding_strategy, truncation_strategy, max_length, kwargs

    @add_end_docstrings(ENCODE_KWARGS_DOCSTRING, ENCODE_PLUS_ADDITIONAL_KWARGS_DOCSTRING)
    def __call__(
        self,
        text: Union[TextInput, PreTokenizedInput, List[TextInput], List[PreTokenizedInput]],
        text_pair: Optional[Union[TextInput, PreTokenizedInput, List[TextInput], List[PreTokenizedInput]]] = None,
        add_special_tokens: bool = True,
        padding: Union[bool, str] = False,
        truncation: Union[bool, str] = False,
        max_length: Optional[int] = None,
        stride: int = 0,
        is_pretokenized: bool = False,
        pad_to_multiple_of: Optional[int] = None,
        return_tensors: Optional[Union[str, TensorType]] = None,
        return_token_type_ids: Optional[bool] = None,
        return_attention_mask: Optional[bool] = None,
        return_overflowing_tokens: bool = False,
        return_special_tokens_mask: bool = False,
        return_offsets_mapping: bool = False,
        return_length: bool = False,
        verbose: bool = True,
        **kwargs
    ) -> BatchEncoding:
        """
        Returns a dictionary containing the encoded sequence or sequence pair and additional information:
        the mask for sequence classification and the overflowing elements if a ``max_length`` is specified.

        Args:
            text (:obj:`str`, :obj:`List[str]`, :obj:`List[List[str]]``):
                The sequence or batch of sequences to be encoded.
                Each sequence can be a string or a list of strings (pre-tokenized string).
                If the sequences are provided as list of strings (pretokenized), you must set `is_pretokenized=True`
                (to lift the ambiguity with a batch of sequences)
            text_pair (:obj:`str`, :obj:`List[str]`, :obj:`List[List[str]]``):
                The sequence or batch of sequences to be encoded.
                Each sequence can be a string or a list of strings (pre-tokenized string).
                If the sequences are provided as list of strings (pretokenized), you must set `is_pretokenized=True`
                (to lift the ambiguity with a batch of sequences)
        """
        # Input type checking for clearer error
        assert isinstance(text, str) or (
            isinstance(text, (list, tuple))
            and (
                len(text) == 0
                or (
                    isinstance(text[0], str)
                    or (isinstance(text[0], (list, tuple)) and (len(text[0]) == 0 or isinstance(text[0][0], str)))
                )
            )
        ), (
            "text input must of type `str` (single example), `List[str]` (batch or single pretokenized example) "
            "or `List[List[str]]` (batch of pretokenized examples)."
        )

        assert (
            text_pair is None
            or isinstance(text_pair, str)
            or (
                isinstance(text_pair, (list, tuple))
                and (
                    len(text_pair) == 0
                    or (
                        isinstance(text_pair[0], str)
                        or (
                            isinstance(text_pair[0], (list, tuple))
                            and (len(text_pair[0]) == 0 or isinstance(text_pair[0][0], str))
                        )
                    )
                )
            )
        ), (
            "text_pair input must of type `str` (single example), `List[str]` (batch or single pretokenized example) "
            "or `List[List[str]]` (batch of pretokenized examples)."
        )

        is_batched = bool(
            (not is_pretokenized and isinstance(text, (list, tuple)))
            or (is_pretokenized and isinstance(text, (list, tuple)) and text and isinstance(text[0], (list, tuple)))
        )

        if is_batched:
            batch_text_or_text_pairs = list(zip(text, text_pair)) if text_pair is not None else text
            return self.batch_encode_plus(
                batch_text_or_text_pairs=batch_text_or_text_pairs,
                add_special_tokens=add_special_tokens,
                padding=padding,
                truncation=truncation,
                max_length=max_length,
                stride=stride,
                is_pretokenized=is_pretokenized,
                pad_to_multiple_of=pad_to_multiple_of,
                return_tensors=return_tensors,
                return_token_type_ids=return_token_type_ids,
                return_attention_mask=return_attention_mask,
                return_overflowing_tokens=return_overflowing_tokens,
                return_special_tokens_mask=return_special_tokens_mask,
                return_offsets_mapping=return_offsets_mapping,
                return_length=return_length,
                verbose=verbose,
                **kwargs,
            )
        else:
            return self.encode_plus(
                text=text,
                text_pair=text_pair,
                add_special_tokens=add_special_tokens,
                padding=padding,
                truncation=truncation,
                max_length=max_length,
                stride=stride,
                is_pretokenized=is_pretokenized,
                pad_to_multiple_of=pad_to_multiple_of,
                return_tensors=return_tensors,
                return_token_type_ids=return_token_type_ids,
                return_attention_mask=return_attention_mask,
                return_overflowing_tokens=return_overflowing_tokens,
                return_special_tokens_mask=return_special_tokens_mask,
                return_offsets_mapping=return_offsets_mapping,
                return_length=return_length,
                verbose=verbose,
                **kwargs,
            )

    @add_end_docstrings(ENCODE_KWARGS_DOCSTRING, ENCODE_PLUS_ADDITIONAL_KWARGS_DOCSTRING)
    def encode_plus(
        self,
        text: Union[TextInput, PreTokenizedInput, EncodedInput],
        text_pair: Optional[Union[TextInput, PreTokenizedInput, EncodedInput]] = None,
        add_special_tokens: bool = True,
        padding: Union[bool, str] = False,
        truncation: Union[bool, str] = False,
        max_length: Optional[int] = None,
        stride: int = 0,
        is_pretokenized: bool = False,
        pad_to_multiple_of: Optional[int] = None,
        return_tensors: Optional[Union[str, TensorType]] = None,
        return_token_type_ids: Optional[bool] = None,
        return_attention_mask: Optional[bool] = None,
        return_overflowing_tokens: bool = False,
        return_special_tokens_mask: bool = False,
        return_offsets_mapping: bool = False,
        return_length: bool = False,
        verbose: bool = True,
        **kwargs
    ) -> BatchEncoding:
        """
        Returns a dictionary containing the encoded sequence or sequence pair and additional information:
        the mask for sequence classification and the overflowing elements if a ``max_length`` is specified.

        Args:
            text (:obj:`str`, :obj:`List[str]` or :obj:`List[int]` (the later only for not-fast tokenizers)):
                The first sequence to be encoded. This can be a string, a list of strings (tokenized string using
                the `tokenize` method) or a list of integers (tokenized string ids using the `convert_tokens_to_ids`
                method)
            text_pair (:obj:`str`, :obj:`List[str]` or :obj:`List[int]`, `optional`, defaults to :obj:`None`):
                Optional second sequence to be encoded. This can be a string, a list of strings (tokenized
                string using the `tokenize` method) or a list of integers (tokenized string ids using the
                `convert_tokens_to_ids` method)
        """

        # Backward compatibility for 'truncation_strategy', 'pad_to_max_length'
        padding_strategy, truncation_strategy, max_length, kwargs = self._get_padding_truncation_strategies(
            padding=padding,
            truncation=truncation,
            max_length=max_length,
            pad_to_multiple_of=pad_to_multiple_of,
            verbose=verbose,
            **kwargs,
        )

        return self._encode_plus(
            text=text,
            text_pair=text_pair,
            add_special_tokens=add_special_tokens,
            padding_strategy=padding_strategy,
            truncation_strategy=truncation_strategy,
            max_length=max_length,
            stride=stride,
            is_pretokenized=is_pretokenized,
            pad_to_multiple_of=pad_to_multiple_of,
            return_tensors=return_tensors,
            return_token_type_ids=return_token_type_ids,
            return_attention_mask=return_attention_mask,
            return_overflowing_tokens=return_overflowing_tokens,
            return_special_tokens_mask=return_special_tokens_mask,
            return_offsets_mapping=return_offsets_mapping,
            return_length=return_length,
            verbose=verbose,
            **kwargs,
        )

    def _encode_plus(
        self,
        text: Union[TextInput, PreTokenizedInput, EncodedInput],
        text_pair: Optional[Union[TextInput, PreTokenizedInput, EncodedInput]] = None,
        add_special_tokens: bool = True,
        padding_strategy: PaddingStrategy = PaddingStrategy.DO_NOT_PAD,
        truncation_strategy: TruncationStrategy = TruncationStrategy.DO_NOT_TRUNCATE,
        max_length: Optional[int] = None,
        stride: int = 0,
        is_pretokenized: bool = False,
        pad_to_multiple_of: Optional[int] = None,
        return_tensors: Optional[Union[str, TensorType]] = None,
        return_token_type_ids: Optional[bool] = None,
        return_attention_mask: Optional[bool] = None,
        return_overflowing_tokens: bool = False,
        return_special_tokens_mask: bool = False,
        return_offsets_mapping: bool = False,
        return_length: bool = False,
        verbose: bool = True,
        **kwargs
    ) -> BatchEncoding:
        raise NotImplementedError

    @add_end_docstrings(ENCODE_KWARGS_DOCSTRING, ENCODE_PLUS_ADDITIONAL_KWARGS_DOCSTRING)
    def batch_encode_plus(
        self,
        batch_text_or_text_pairs: Union[
            List[TextInput],
            List[TextInputPair],
            List[PreTokenizedInput],
            List[PreTokenizedInputPair],
            List[EncodedInput],
            List[EncodedInputPair],
        ],
        add_special_tokens: bool = True,
        padding: Union[bool, str] = False,
        truncation: Union[bool, str] = False,
        max_length: Optional[int] = None,
        stride: int = 0,
        is_pretokenized: bool = False,
        pad_to_multiple_of: Optional[int] = None,
        return_tensors: Optional[Union[str, TensorType]] = None,
        return_token_type_ids: Optional[bool] = None,
        return_attention_mask: Optional[bool] = None,
        return_overflowing_tokens: bool = False,
        return_special_tokens_mask: bool = False,
        return_offsets_mapping: bool = False,
        return_length: bool = False,
        verbose: bool = True,
        **kwargs
    ) -> BatchEncoding:
        """
        Returns a dictionary containing the encoded sequence or sequence pair and additional information:
        the mask for sequence classification and the overflowing elements if a ``max_length`` is specified.

        Args:
            batch_text_or_text_pairs (:obj:`List[str]`,  :obj:`List[Tuple[str, str]]`,
                                      :obj:`List[List[str]]`,  :obj:`List[Tuple[List[str], List[str]]]`,
                                      and for not-fast tokenizers, also:
                                      :obj:`List[List[int]]`,  :obj:`List[Tuple[List[int], List[int]]]`):
                Batch of sequences or pair of sequences to be encoded.
                This can be a list of string/string-sequences/int-sequences or a list of pair of
                string/string-sequences/int-sequence (see details in encode_plus)
        """

        # Backward compatibility for 'truncation_strategy', 'pad_to_max_length'
        padding_strategy, truncation_strategy, max_length, kwargs = self._get_padding_truncation_strategies(
            padding=padding,
            truncation=truncation,
            max_length=max_length,
            pad_to_multiple_of=pad_to_multiple_of,
            verbose=verbose,
            **kwargs,
        )

        return self._batch_encode_plus(
            batch_text_or_text_pairs=batch_text_or_text_pairs,
            add_special_tokens=add_special_tokens,
            padding_strategy=padding_strategy,
            truncation_strategy=truncation_strategy,
            max_length=max_length,
            stride=stride,
            is_pretokenized=is_pretokenized,
            pad_to_multiple_of=pad_to_multiple_of,
            return_tensors=return_tensors,
            return_token_type_ids=return_token_type_ids,
            return_attention_mask=return_attention_mask,
            return_overflowing_tokens=return_overflowing_tokens,
            return_special_tokens_mask=return_special_tokens_mask,
            return_offsets_mapping=return_offsets_mapping,
            return_length=return_length,
            verbose=verbose,
            **kwargs,
        )

    def _batch_encode_plus(
        self,
        batch_text_or_text_pairs: Union[
            List[TextInput],
            List[TextInputPair],
            List[PreTokenizedInput],
            List[PreTokenizedInputPair],
            List[EncodedInput],
            List[EncodedInputPair],
        ],
        add_special_tokens: bool = True,
        padding_strategy: PaddingStrategy = PaddingStrategy.DO_NOT_PAD,
        truncation_strategy: TruncationStrategy = TruncationStrategy.DO_NOT_TRUNCATE,
        max_length: Optional[int] = None,
        stride: int = 0,
        is_pretokenized: bool = False,
        pad_to_multiple_of: Optional[int] = None,
        return_tensors: Optional[Union[str, TensorType]] = None,
        return_token_type_ids: Optional[bool] = None,
        return_attention_mask: Optional[bool] = None,
        return_overflowing_tokens: bool = False,
        return_special_tokens_mask: bool = False,
        return_offsets_mapping: bool = False,
        return_length: bool = False,
        verbose: bool = True,
        **kwargs
    ) -> BatchEncoding:
        raise NotImplementedError

    def pad(
        self,
        encoded_inputs: Union[
            BatchEncoding,
            List[BatchEncoding],
            Dict[str, EncodedInput],
            Dict[str, List[EncodedInput]],
            List[Dict[str, EncodedInput]],
        ],
        padding: Union[bool, str] = True,
        max_length: Optional[int] = None,
        pad_to_multiple_of: Optional[int] = None,
        return_attention_mask: Optional[bool] = None,
        return_tensors: Optional[Union[str, TensorType]] = None,
        verbose: bool = True,
    ) -> BatchEncoding:
        """ Pad a single encoded input or a batch of encoded inputs up to predefined length or to the max sequence length in the batch.

            Padding side (left/right) padding token ids are defined at the tokenizer level
            (with ``self.padding_side``, ``self.pad_token_id`` and ``self.pad_token_type_id``)

        Args:
            encoded_inputs: Dictionary of tokenized inputs (`Dict[str, List[int]]`) or batch of tokenized inputs.
                Batch of tokenized inputs can be given as dicts of lists or lists of dicts, both work so you can
                use ``tokenizer.pad()`` during pre-processing as well as in a PyTorch Dataloader collate function.
                (`Dict[str, List[List[int]]]` or `List[Dict[str, List[int]]]`).
            padding: Boolean or specific strategy to use for padding.
                Select a strategy to pad the returned sequences (according to the model's padding side and padding index) among:
                - 'longest' (or `True`) Pad to the longest sequence in the batch
                - 'max_length': Pad to the max length (default)
                - 'do_not_pad' (or `False`): Do not pad
            max_length: maximum length of the returned list and optionally padding length (see below).
                Will truncate by taking into account the special tokens.
            pad_to_multiple_of: (optional) Integer if set will pad the sequence to a multiple of the provided value.
                This is especially useful to enable the use of Tensor Core on NVIDIA hardware with compute capability
                >= 7.5 (Volta).
            return_attention_mask: (optional) Set to False to avoid returning attention mask (default: set to model specifics)
            return_tensors (:obj:`str`, `optional`, defaults to :obj:`None`):
                Can be set to 'tf', 'pt' or 'np' to return respectively TensorFlow :obj:`tf.constant`,
                PyTorch :obj:`torch.Tensor` or Numpy :oj: `np.ndarray` instead of a list of python integers.
            verbose (:obj:`bool`, `optional`, defaults to :obj:`True`):
                Set to ``False`` to avoid printing infos and warnings.
        """
        # If we have a list of dicts, let's convert it in a dict of lists
        if isinstance(encoded_inputs, (list, tuple)) and isinstance(encoded_inputs[0], (dict, BatchEncoding)):
            encoded_inputs = {key: [example[key] for example in encoded_inputs] for key in encoded_inputs[0].keys()}

        assert "input_ids" in encoded_inputs, (
            "You should supply an encoding or a list of encodings to this method. "
            "An encoding is the output of one the encoding methods of the tokenizer, i.e. "
            "__call__/encode_plus/batch_encode_plus. "
        )

        if not encoded_inputs["input_ids"]:
            if return_attention_mask:
                encoded_inputs["attention_mask"] = []
            return encoded_inputs

        # Convert padding_strategy in PaddingStrategy
        padding_strategy, _, max_length, _ = self._get_padding_truncation_strategies(
            padding=padding, max_length=max_length, verbose=verbose
        )

        if encoded_inputs["input_ids"] and not isinstance(encoded_inputs["input_ids"][0], (list, tuple)):
            encoded_inputs = self._pad(
                encoded_inputs,
                max_length=max_length,
                padding_strategy=padding_strategy,
                pad_to_multiple_of=pad_to_multiple_of,
                return_attention_mask=return_attention_mask,
            )
            return BatchEncoding(encoded_inputs, tensor_type=return_tensors)

        batch_size = len(encoded_inputs["input_ids"])
        assert all(
            len(v) == batch_size for v in encoded_inputs.values()
        ), "Some items in the output dictionnary have a different batch size than others."

        if padding_strategy == PaddingStrategy.LONGEST:
            max_length = max(len(inputs) for inputs in encoded_inputs["input_ids"])
            padding_strategy = PaddingStrategy.MAX_LENGTH

        batch_outputs = {}
        for i in range(batch_size):
            inputs = dict((k, v[i]) for k, v in encoded_inputs.items())
            outputs = self._pad(
                inputs,
                max_length=max_length,
                padding_strategy=padding_strategy,
                pad_to_multiple_of=pad_to_multiple_of,
                return_attention_mask=return_attention_mask,
            )

            for key, value in outputs.items():
                if key not in batch_outputs:
                    batch_outputs[key] = []
                batch_outputs[key].append(value)

        return BatchEncoding(batch_outputs, tensor_type=return_tensors)

    def create_token_type_ids_from_sequences(self, token_ids_0: List, token_ids_1: Optional[List] = None) -> List[int]:
        if token_ids_1 is None:
            return len(token_ids_0) * [0]
        return [0] * len(token_ids_0) + [1] * len(token_ids_1)

    def build_inputs_with_special_tokens(self, token_ids_0: List, token_ids_1: Optional[List] = None) -> List:
        """
        Build model inputs from a sequence or a pair of sequence for sequence classification tasks
        by concatenating and adding special tokens. This implementation does not add special tokens.
        """
        if token_ids_1 is None:
            return token_ids_0
        return token_ids_0 + token_ids_1

    @add_end_docstrings(ENCODE_KWARGS_DOCSTRING, ENCODE_PLUS_ADDITIONAL_KWARGS_DOCSTRING)
    def prepare_for_model(
        self,
        ids: List[int],
        pair_ids: Optional[List[int]] = None,
        add_special_tokens: bool = True,
        padding: Union[bool, str] = False,
        truncation: Union[bool, str] = False,
        max_length: Optional[int] = None,
        stride: int = 0,
        pad_to_multiple_of: Optional[int] = None,
        return_tensors: Optional[Union[str, TensorType]] = None,
        return_token_type_ids: Optional[bool] = None,
        return_attention_mask: Optional[bool] = None,
        return_overflowing_tokens: bool = False,
        return_special_tokens_mask: bool = False,
        return_offsets_mapping: bool = False,
        return_length: bool = False,
        verbose: bool = True,
        prepend_batch_axis: bool = False,
        **kwargs
    ) -> BatchEncoding:
        """ Prepares a sequence of input id, or a pair of sequences of inputs ids so that it can be used by the model.
        It adds special tokens, truncates sequences if overflowing while taking into account the special tokens and
        manages a moving window (with user defined stride) for overflowing tokens

        Args:
            ids: list of tokenized input ids. Can be obtained from a string by chaining the
                `tokenize` and `convert_tokens_to_ids` methods.
            pair_ids: Optional second list of input ids. Can be obtained from a string by chaining the
                `tokenize` and `convert_tokens_to_ids` methods.
        """

        if "return_lengths" in kwargs:
            if verbose:
                warnings.warn(
                    "The PreTrainedTokenizerBase.prepare_for_model `return_lengths` parameter is deprecated. "
                    "Please use `return_length` instead.",
                    FutureWarning,
                )
            return_length = kwargs["return_lengths"]

        # Backward compatibility for 'truncation_strategy', 'pad_to_max_length'
        padding_strategy, truncation_strategy, max_length, kwargs = self._get_padding_truncation_strategies(
            padding=padding,
            truncation=truncation,
            max_length=max_length,
            pad_to_multiple_of=pad_to_multiple_of,
            verbose=verbose,
            **kwargs,
        )

        pair = bool(pair_ids is not None)
        len_ids = len(ids)
        len_pair_ids = len(pair_ids) if pair else 0

        # Load from model defaults
        if return_token_type_ids is None:
            return_token_type_ids = "token_type_ids" in self.model_input_names
        if return_attention_mask is None:
            return_attention_mask = "attention_mask" in self.model_input_names

        encoded_inputs = {}

        # Compute the total size of the returned encodings
        total_len = len_ids + len_pair_ids + (self.num_special_tokens_to_add(pair=pair) if add_special_tokens else 0)

        # Truncation: Handle max sequence length
        if truncation_strategy != TruncationStrategy.DO_NOT_TRUNCATE and max_length and total_len > max_length:
            ids, pair_ids, overflowing_tokens = self.truncate_sequences(
                ids,
                pair_ids=pair_ids,
                num_tokens_to_remove=total_len - max_length,
                truncation_strategy=truncation_strategy,
                stride=stride,
            )
            if return_overflowing_tokens:
                encoded_inputs["overflowing_tokens"] = overflowing_tokens
                encoded_inputs["num_truncated_tokens"] = total_len - max_length

        # Add special tokens
        if add_special_tokens:
            sequence = self.build_inputs_with_special_tokens(ids, pair_ids)
            token_type_ids = self.create_token_type_ids_from_sequences(ids, pair_ids)
        else:
            sequence = ids + pair_ids if pair else ids
            token_type_ids = [0] * len(ids) + ([1] * len(pair_ids) if pair else [])

        # Build output dictionnary
        encoded_inputs["input_ids"] = sequence
        if return_token_type_ids:
            encoded_inputs["token_type_ids"] = token_type_ids
        if return_special_tokens_mask:
            if add_special_tokens:
                encoded_inputs["special_tokens_mask"] = self.get_special_tokens_mask(ids, pair_ids)
            else:
                encoded_inputs["special_tokens_mask"] = [0] * len(sequence)

        # Check lengths
        if max_length is None and len(encoded_inputs["input_ids"]) > self.model_max_length and verbose:
            logger.warning(
                "Token indices sequence length is longer than the specified maximum sequence length "
                "for this model ({} > {}). Running this sequence through the model will result in "
                "indexing errors".format(len(ids), self.model_max_length)
            )

        # Padding
        if padding_strategy != PaddingStrategy.DO_NOT_PAD or return_attention_mask:
            encoded_inputs = self.pad(
                encoded_inputs,
                max_length=max_length,
                padding=padding_strategy.value,
                pad_to_multiple_of=pad_to_multiple_of,
                return_attention_mask=return_attention_mask,
            )

        if return_length:
            encoded_inputs["length"] = len(encoded_inputs["input_ids"])

        batch_outputs = BatchEncoding(
            encoded_inputs, tensor_type=return_tensors, prepend_batch_axis=prepend_batch_axis
        )

        return batch_outputs

    def truncate_sequences(
        self,
        ids: List[int],
        pair_ids: Optional[List[int]] = None,
        num_tokens_to_remove: int = 0,
        truncation_strategy: Union[str, TruncationStrategy] = "longest_first",
        stride: int = 0,
    ) -> Tuple[List[int], List[int], List[int]]:
        """ Truncates a sequence pair in place to the maximum length.

        Args:
            ids: list of tokenized input ids. Can be obtained from a string by chaining the
                `tokenize` and `convert_tokens_to_ids` methods.
            pair_ids: Optional second list of input ids. Can be obtained from a string by chaining the
                `tokenize` and `convert_tokens_to_ids` methods.
            num_tokens_to_remove (:obj:`int`, `optional`, defaults to ``0``):
                number of tokens to remove using the truncation strategy
            truncation_strategy (:obj:`string`, `optional`, defaults to "longest_first"):
                String selected in the following options:

                - 'longest_first' (default): Iteratively reduce the inputs sequence until the input is under max_length
                  starting from the longest one at each token (when there is a pair of input sequences).
                  Overflowing tokens only contains overflow from the first sequence.
                - 'only_first': Only truncate the first sequence. raise an error if the first sequence is shorter or equal to than num_tokens_to_remove.
                - 'only_second': Only truncate the second sequence
                - 'do_not_truncate'
            stride (:obj:`int`, `optional`, defaults to ``0``):
                If set to a number along with max_length, the overflowing tokens returned will contain some tokens
                from the main sequence returned. The value of this argument defines the number of additional tokens.
        """
        if num_tokens_to_remove <= 0:
            return ids, pair_ids, []

        if not isinstance(truncation_strategy, TruncationStrategy):
            truncation_strategy = TruncationStrategy(truncation_strategy)

        overflowing_tokens = []
        if truncation_strategy == TruncationStrategy.LONGEST_FIRST:
            for _ in range(num_tokens_to_remove):
                if pair_ids is None or len(ids) > len(pair_ids):
                    if not overflowing_tokens:
                        window_len = min(len(ids), stride + 1)
                    else:
                        window_len = 1
                    overflowing_tokens.extend(ids[-window_len:])
                    ids = ids[:-1]
                else:
                    if not overflowing_tokens:
                        window_len = min(len(pair_ids), stride + 1)
                    else:
                        window_len = 1
                    overflowing_tokens.extend(pair_ids[-window_len:])
                    pair_ids = pair_ids[:-1]
        elif truncation_strategy == TruncationStrategy.ONLY_FIRST:
            if len(ids) > num_tokens_to_remove:
                window_len = min(len(ids), stride + num_tokens_to_remove)
                overflowing_tokens = ids[-window_len:]
                ids = ids[:-num_tokens_to_remove]
            else:
                logger.error(
                    f"We need to remove {num_tokens_to_remove} to truncate the input"
                    f"but the first sequence has a length {len(ids)}. "
                    f"Please select another truncation strategy than {truncation_strategy}, "
                    f"for instance 'longest_first' or 'only_second'."
                )
        elif truncation_strategy == TruncationStrategy.ONLY_SECOND and pair_ids is not None:
            if len(pair_ids) > num_tokens_to_remove:
                window_len = min(len(pair_ids), stride + num_tokens_to_remove)
                overflowing_tokens = pair_ids[-window_len:]
                pair_ids = pair_ids[:-num_tokens_to_remove]
            else:
                logger.error(
                    f"We need to remove {num_tokens_to_remove} to truncate the input"
                    f"but the second sequence has a length {len(pair_ids)}. "
                    f"Please select another truncation strategy than {truncation_strategy}, "
                    f"for instance 'longest_first' or 'only_first'."
                )

        return (ids, pair_ids, overflowing_tokens)

    def _pad(
        self,
        encoded_inputs: Union[Dict[str, EncodedInput], BatchEncoding],
        max_length: Optional[int] = None,
        padding_strategy: PaddingStrategy = PaddingStrategy.DO_NOT_PAD,
        pad_to_multiple_of: Optional[int] = None,
        return_attention_mask: Optional[bool] = None,
    ) -> dict:
        """ Pad encoded inputs (on left/right and up to predefined legnth or max length in the batch)

        Args:
            encoded_inputs: Dictionary of tokenized inputs (`List[int]`) or batch of tokenized inputs (`List[List[int]]`).
            max_length: maximum length of the returned list and optionally padding length (see below).
                Will truncate by taking into account the special tokens.
            padding_strategy: PaddingStrategy to use for padding.
                - PaddingStrategy.LONGEST Pad to the longest sequence in the batch
                - PaddingStrategy.MAX_LENGTH: Pad to the max length (default)
                - PaddingStrategy.DO_NOT_PAD: Do not pad
                The tokenizer padding sides are defined in self.padding_side:
                    - 'left': pads on the left of the sequences
                    - 'right': pads on the right of the sequences
            pad_to_multiple_of: (optional) Integer if set will pad the sequence to a multiple of the provided value.
                This is especially useful to enable the use of Tensor Core on NVIDIA hardware with compute capability
                >= 7.5 (Volta).
            return_attention_mask: (optional) Set to False to avoid returning attention mask (default: set to model specifics)
        """
        # Load from model defaults
        if return_attention_mask is None:
            return_attention_mask = "attention_mask" in self.model_input_names

        if padding_strategy == PaddingStrategy.LONGEST:
            max_length = len(encoded_inputs["input_ids"])

        if max_length is not None and pad_to_multiple_of is not None and (max_length % pad_to_multiple_of != 0):
            max_length = ((max_length // pad_to_multiple_of) + 1) * pad_to_multiple_of

        needs_to_be_padded = (
            padding_strategy != PaddingStrategy.DO_NOT_PAD and len(encoded_inputs["input_ids"]) != max_length
        )

        if needs_to_be_padded:
            difference = max_length - len(encoded_inputs["input_ids"])
            if self.padding_side == "right":
                if return_attention_mask:
                    encoded_inputs["attention_mask"] = [1] * len(encoded_inputs["input_ids"]) + [0] * difference
                if "token_type_ids" in encoded_inputs:
                    encoded_inputs["token_type_ids"] = (
                        encoded_inputs["token_type_ids"] + [self.pad_token_type_id] * difference
                    )
                if "special_tokens_mask" in encoded_inputs:
                    encoded_inputs["special_tokens_mask"] = encoded_inputs["special_tokens_mask"] + [1] * difference
                encoded_inputs["input_ids"] = encoded_inputs["input_ids"] + [self.pad_token_id] * difference
            elif self.padding_side == "left":
                if return_attention_mask:
                    encoded_inputs["attention_mask"] = [0] * difference + [1] * len(encoded_inputs["input_ids"])
                if "token_type_ids" in encoded_inputs:
                    encoded_inputs["token_type_ids"] = [self.pad_token_type_id] * difference + encoded_inputs[
                        "token_type_ids"
                    ]
                if "special_tokens_mask" in encoded_inputs:
                    encoded_inputs["special_tokens_mask"] = [1] * difference + encoded_inputs["special_tokens_mask"]
                encoded_inputs["input_ids"] = [self.pad_token_id] * difference + encoded_inputs["input_ids"]
            else:
                raise ValueError("Invalid padding strategy:" + str(self.padding_side))
        else:
            if return_attention_mask:
                encoded_inputs["attention_mask"] = [1] * len(encoded_inputs["input_ids"])

        return encoded_inputs

    def batch_decode(self, sequences: List[List[int]], **kwargs) -> List[str]:
        return [self.decode(seq, **kwargs) for seq in sequences]

    def decode(
        self, token_ids: List[int], skip_special_tokens: bool = False, clean_up_tokenization_spaces: bool = True
    ) -> str:
        """
        Converts a sequence of ids (integer) in a string, using the tokenizer and vocabulary
        with options to remove special tokens and clean up tokenization spaces.
        Similar to doing ``self.convert_tokens_to_string(self.convert_ids_to_tokens(token_ids))``.

        Args:
            token_ids: list of tokenized input ids. Can be obtained using the `encode` or `encode_plus` methods.
            skip_special_tokens: if set to True, will replace special tokens.
            clean_up_tokenization_spaces: if set to True, will clean up the tokenization spaces.
        """
        raise NotImplementedError

    def get_special_tokens_mask(
        self, token_ids_0: List, token_ids_1: Optional[List] = None, already_has_special_tokens: bool = False
    ) -> List[int]:
        """
        Retrieves sequence ids from a token list that has no special tokens added. This method is called when adding
        special tokens using the tokenizer ``prepare_for_model`` or ``encode_plus`` methods.

        Args:
            token_ids_0: list of ids (must not contain special tokens)
            token_ids_1: Optional list of ids (must not contain special tokens), necessary when fetching sequence ids
                for sequence pairs
            already_has_special_tokens: (default False) Set to True if the token list is already formated with
                special tokens for the model

        Returns:
            A list of integers in the range [0, 1]: 1 for a special token, 0 for a sequence token.
        """
        assert already_has_special_tokens and token_ids_1 is None, (
            "You cannot use ``already_has_special_tokens=False`` with this tokenizer. "
            "Please use a slow (full python) tokenizer to activate this argument."
            "Or set `return_special_token_mask=True` when calling the encoding method "
            "to get the special tokens mask in any tokenizer. "
        )

        all_special_ids = self.all_special_ids  # cache the property

        special_tokens_mask = [1 if token in all_special_ids else 0 for token in token_ids_0]

        return special_tokens_mask

    @staticmethod
    def clean_up_tokenization(out_string: str) -> str:
        """ Clean up a list of simple English tokenization artifacts like spaces before punctuations and abreviated forms.
        """
        out_string = (
            out_string.replace(" .", ".")
            .replace(" ?", "?")
            .replace(" !", "!")
            .replace(" ,", ",")
            .replace(" ' ", "'")
            .replace(" n't", "n't")
            .replace(" 'm", "'m")
            .replace(" 's", "'s")
            .replace(" 've", "'ve")
            .replace(" 're", "'re")
        )
        return out_string