Update FastChemTokenizerHF2.py

FastChemTokenizerHF2.py

@@ -1,813 +1,580 @@
-import torch
-import json
-import os
-from typing import List, Union, Optional, Tuple, Dict, Any
-from functools import lru_cache
-
-# Minimal equivalents for problematic imports
-class BatchEncoding:
-    def __init__(self, data, tensor_type=None):
-        self.data = data
-        for key, value in data.items():
-            setattr(self, key, value)
-    
-    def __getitem__(self, key):
-        return self.data[key]
-    
-    def __contains__(self, key):
-        return key in self.data  # This should fix the issue
-    
-    def keys(self):
-        return self.data.keys()
-    
-    def values(self):
-        return self.data.values()
-    
-    def items(self):
-        return self.data.items()
-class PreTrainedTokenizerBase:
-    def __init__(self, **kwargs):
-        # Set special tokens from kwargs
-        for key, value in kwargs.items():
-            if key.endswith('_token'):
-                setattr(self, f"_{key}", value)
-                # Don't set token_id here - let subclass handle it
-        
-        # Set other attributes
-        self.model_max_length = kwargs.get('model_max_length', 512)
-        self.padding_side = kwargs.get('padding_side', 'right')
-        self.truncation_side = kwargs.get('truncation_side', 'right')
-        self.chat_template = kwargs.get('chat_template')
-
-class TrieNode:
-    __slots__ = ['children', 'token_id']
-    def __init__(self):
-        self.children = {}
-        self.token_id = None  # If set, this node completes a valid token
-
-class FastChemTokenizer(PreTrainedTokenizerBase):
-    """
-    Fully HuggingFace API compatible tokenizer for chemical representations.
-    """
-    
-    def __init__(
-        self,
-        token_to_id=None,
-        vocab_file=None,
-        model_max_length=512,
-        padding_side="right",
-        truncation_side="right",
-        chat_template=None,
-        **kwargs
-    ):
-        # Handle vocab loading
-        if token_to_id is None and vocab_file is None:
-            raise ValueError("Either token_to_id or vocab_file must be provided")
-
-        if vocab_file is not None:
-            with open(vocab_file, "r", encoding="utf-8") as f:
-                token_to_id = json.load(f)
-                token_to_id = {str(k): int(v) for k, v in token_to_id.items()}
-
-        self.token_to_id = token_to_id
-        self.id_to_token = {v: k for k, v in token_to_id.items()}
-
-        # Precompute max token length for possible use & clarity
-        self.max_token_len = max(len(t) for t in token_to_id.keys()) if token_to_id else 0
-
-        # Build trie for fast longest-match lookup
-        self.trie_root = self._build_trie(token_to_id)
-
-        # Validate required special tokens
-        required_special_tokens = ["<s>", "</s>", "<pad>", "<unk>", "<mask>"]
-        for tok in required_special_tokens:
-            if tok not in token_to_id:
-                raise KeyError(f"Required special token '{tok}' not found in vocab.")
-
-        # ✅ Assign special token IDs explicitly - MUST be done before parent init
-        self.bos_token_id = token_to_id["<s>"]
-        self.eos_token_id = token_to_id["</s>"]
-        self.pad_token_id = token_to_id["<pad>"]
-        self.unk_token_id = token_to_id["<unk>"]
-        self.mask_token_id = token_to_id["<mask>"]
-
-        # Initialize parent class
-        super().__init__(
-            bos_token="<s>",
-            eos_token="</s>",
-            unk_token="<unk>",
-            sep_token=None,
-            pad_token="<pad>",
-            cls_token=None,
-            mask_token="<mask>",
-            additional_special_tokens=[],
-            model_max_length=model_max_length,
-            padding_side=padding_side,
-            truncation_side=truncation_side,
-            chat_template=chat_template,
-            **kwargs,
-        )
-
-        # ✅ Set all token attributes for compatibility
-        self._unk_token = "<unk>"
-        self._bos_token = "<s>"
-        self._eos_token = "</s>"
-        self._pad_token = "<pad>"
-        self._mask_token = "<mask>"
-        self._sep_token = None
-        self._cls_token = None
-        
-        self.unk_token = "<unk>"
-        self.bos_token = "<s>"
-        self.eos_token = "</s>"
-        self.pad_token = "<pad>"
-        self.mask_token = "<mask>"
-        self.sep_token = None
-        self.cls_token = None
-
-    def _build_trie(self, token_to_id):
-        root = TrieNode()
-        for token, tid in token_to_id.items():
-            node = root
-            for char in token:
-                if char not in node.children:
-                    node.children[char] = TrieNode()
-                node = node.children[char]
-            node.token_id = tid
-        return root
-
-    @property
-    def vocab_size(self):
-        return len(self.token_to_id)
-
-    def __len__(self):
-        return len(self.token_to_id)
-
-    def get_vocab(self) -> Dict[str, int]:
-        return self.token_to_id.copy()
-
-    @lru_cache(maxsize=10000)
-    def _cached_encode_str(self, s: str) -> Tuple[int, ...]:
-        return tuple(self._encode_core(s))
-
-    def _encode_core(self, text: str) -> List[int]:
-        """Core encoding logic using Trie — no caching."""
-        tokens = text
-        result_ids = []
-        i = 0
-        n = len(tokens)
-
-        while i < n:
-            node = self.trie_root
-            j = i
-            last_match_id = None
-            last_match_end = i
-
-            while j < n and tokens[j] in node.children:
-                node = node.children[tokens[j]]
-                j += 1
-                if node.token_id is not None:
-                    last_match_id = node.token_id
-                    last_match_end = j
-
-            if last_match_id is not None:
-                result_ids.append(last_match_id)
-                i = last_match_end
-            else:
-                tok = tokens[i]
-                result_ids.append(self.token_to_id.get(tok, self.unk_token_id))
-                i += 1
-
-        return result_ids
-
-    def _tokenize(self, text: str, **kwargs) -> List[str]:
-        token_ids = self._encode_core(text.strip())
-        return [self.id_to_token[tid] for tid in token_ids]
-
-    def _convert_token_to_id(self, token: str) -> int:
-        return self.token_to_id.get(token, self.unk_token_id)
-
-    def _convert_id_to_token(self, index: int) -> str:
-        return self.id_to_token.get(index, self.unk_token)
-
-    # ✅ Public methods
-    def convert_tokens_to_ids(self, tokens: Union[str, List[str]]) -> Union[int, List[int]]:
-        if isinstance(tokens, str):
-            return self._convert_token_to_id(tokens)
-        return [self._convert_token_to_id(tok) for tok in tokens]
-
-    def convert_ids_to_tokens(self, ids: Union[int, List[int]]) -> Union[str, List[str]]:
-        if isinstance(ids, int):
-            return self._convert_id_to_token(ids)
-        return [self._convert_id_to_token(i) for i in ids]
-
-    def convert_tokens_to_string(self, tokens: List[str]) -> str:
-        """SMILES-style decoding: no spaces between tokens."""
-        return "".join(tokens)
-
-    def encode(
-        self,
-        text: str,
-        text_pair: Optional[str] = None,
-        add_special_tokens: bool = True,
-        padding: bool = False,
-        truncation: bool = False,
-        max_length: Optional[int] = None,
-        return_tensors: Optional[str] = None,
-    ) -> List[int]:
-        """Simple encode method that returns list of token IDs."""
-        if text_pair is not None:
-            raise NotImplementedError("text_pair not supported in simple encode method")
-        
-        # Get core token IDs
-        token_ids = list(self._cached_encode_str(text.strip()))
-        
-        # Add special tokens if requested
-        if add_special_tokens:
-            token_ids = [self.bos_token_id] + token_ids + [self.eos_token_id]
-        
-        # Handle truncation
-        if truncation:
-            if max_length is None:
-                max_length = self.model_max_length
-            if len(token_ids) > max_length:
-                token_ids = token_ids[:max_length]
-        
-        # Handle padding
-        if padding:
-            if max_length is None:
-                max_length = self.model_max_length
-            pad_len = max_length - len(token_ids)
-            if pad_len > 0:
-                if self.padding_side == "right":
-                    token_ids = token_ids + [self.pad_token_id] * pad_len
-                else:
-                    token_ids = [self.pad_token_id] * pad_len + token_ids
-        
-        # Return as tensor if requested
-        if return_tensors == "pt":
-            token_ids = torch.tensor(token_ids, dtype=torch.long)
-            if token_ids.dim() == 0:  # scalar
-                token_ids = token_ids.unsqueeze(0)
-        
-        return token_ids
-
-    def decode(
-        self,
-        token_ids: Union[List[int], torch.Tensor],
-        skip_special_tokens: bool = False,
-        clean_up_tokenization_spaces: bool = None,
-        **kwargs
-    ) -> str:
-        if isinstance(token_ids, torch.Tensor):
-            token_ids = token_ids.tolist()
-
-        if skip_special_tokens:
-            special_ids = {
-                self.bos_token_id,
-                self.eos_token_id,
-                self.pad_token_id,
-                self.mask_token_id,
-            }
-        else:
-            special_ids = set()
-
-        tokens = []
-        for tid in token_ids:
-            if tid in special_ids:
-                continue
-            token = self.id_to_token.get(tid, self.unk_token)
-            tokens.append(token)
-
-        return "".join(tokens)
-    
-    def batch_decode(
-        self,
-        sequences: Union[List[List[int]], torch.Tensor],
-        skip_special_tokens: bool = False,
-        clean_up_tokenization_spaces: bool = None,
-        **kwargs
-    ) -> List[str]:
-        """Batch decode sequences."""
-        if isinstance(sequences, torch.Tensor):
-            sequences = sequences.tolist()
-        
-        return [
-            self.decode(
-                seq, 
-                skip_special_tokens=skip_special_tokens,
-                clean_up_tokenization_spaces=clean_up_tokenization_spaces,
-                **kwargs
-            ) 
-            for seq in sequences
-        ]
-
-    def decode_with_trace(self, token_ids: List[int]) -> None:
-        """Debug method to trace decoding process."""
-        print(f"\n🔍 Decoding {len(token_ids)} tokens:")
-        for i, tid in enumerate(token_ids):
-            token = self.id_to_token.get(tid, self.unk_token)
-            print(f"  [{i:03d}] ID={tid:5d} → '{token}'")
-
-    def __call__(
-        self, 
-        text: Union[str, List[str]], 
-        text_pair: Optional[Union[str, List[str]]] = 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_split_into_words: bool = False,
-        pad_to_multiple_of: Optional[int] = None,
-        return_tensors: Optional[Union[str, Any]] = 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:
-        """
-        Main callable method that handles both single and batch inputs.
-        """
-        # Handle defaults
-        if return_token_type_ids is None:
-            return_token_type_ids = True
-        if return_attention_mask is None:
-            return_attention_mask = True
-            
-        if isinstance(text, list):
-            if text_pair is not None:
-                batch = [(t, p) for t, p in zip(text, text_pair)]
-            else:
-                batch = text
-            return self.batch_encode_plus(
-                batch, 
-                add_special_tokens=add_special_tokens,
-                padding=padding,
-                truncation=truncation,
-                max_length=max_length,
-                stride=stride,
-                is_split_into_words=is_split_into_words,
-                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_split_into_words=is_split_into_words,
-                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: str,
-        text_pair: Optional[str] = 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_split_into_words: bool = False,
-        pad_to_multiple_of: Optional[int] = None,
-        return_tensors: Optional[Union[str, Any]] = None,
-        return_token_type_ids: Optional[bool] = True,
-        return_attention_mask: Optional[bool] = True,
-        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:
-        if max_length is None:
-            max_length = self.model_max_length
-
-        ids_a = list(self._cached_encode_str(text.strip()))
-
-        if text_pair is not None:
-            ids_b = list(self._cached_encode_str(text_pair.strip()))
-        else:
-            ids_b = None
-
-        input_ids = []
-        token_type_ids = []
-
-        if add_special_tokens:
-            input_ids.append(self.bos_token_id)
-            token_type_ids.append(0)
-            if ids_b is not None:
-                input_ids.extend(ids_a)
-                token_type_ids.extend([0] * len(ids_a))
-                input_ids.append(self.eos_token_id)
-                token_type_ids.append(0)
-
-                input_ids.extend(ids_b)
-                token_type_ids.extend([1] * len(ids_b))
-                input_ids.append(self.eos_token_id)
-                token_type_ids.append(1)
-            else:
-                input_ids.extend(ids_a)
-                token_type_ids.extend([0] * len(ids_a))
-                input_ids.append(self.eos_token_id)
-                token_type_ids.append(0)
-        else:
-            input_ids = ids_a.copy()
-            token_type_ids = [0] * len(input_ids)
-            if ids_b is not None:
-                input_ids.extend(ids_b)
-                token_type_ids.extend([1] * len(ids_b))
-
-        # Handle truncation
-        if truncation and len(input_ids) > max_length:
-            input_ids = input_ids[:max_length]
-            token_type_ids = token_type_ids[:max_length]
-
-        # Handle padding
-        if padding == True or padding == "max_length":
-            pad_len = max_length - len(input_ids)
-            if pad_len > 0:
-                if self.padding_side == "right":
-                    input_ids.extend([self.pad_token_id] * pad_len)
-                    token_type_ids.extend([0] * pad_len)
-                else:
-                    input_ids = [self.pad_token_id] * pad_len + input_ids
-                    token_type_ids = [0] * pad_len + token_type_ids
-
-        attention_mask = [1 if tid != self.pad_token_id else 0 for tid in input_ids]
-
-        encoded_dict = {
-            "input_ids": input_ids,
-        }
-        
-        if return_attention_mask:
-            encoded_dict["attention_mask"] = attention_mask
-        
-        if return_token_type_ids:
-            encoded_dict["token_type_ids"] = token_type_ids
-            
-        if return_special_tokens_mask:
-            special_tokens_mask = [
-                1 if tid in {self.bos_token_id, self.eos_token_id, self.pad_token_id, self.mask_token_id} else 0 
-                for tid in input_ids
-            ]
-            encoded_dict["special_tokens_mask"] = special_tokens_mask
-            
-        if return_length:
-            encoded_dict["length"] = len([tid for tid in input_ids if tid != self.pad_token_id])
-
-        if return_tensors == "pt":
-            output = {}
-            for k, v in encoded_dict.items():
-                tensor = torch.tensor(v, dtype=torch.long)
-                if tensor.ndim == 1:
-                    tensor = tensor.unsqueeze(0)
-                output[k] = tensor
-        else:
-            output = encoded_dict
-
-        return BatchEncoding(output, tensor_type=return_tensors)
-
-    def batch_encode_plus(
-        self,
-        batch_text_or_text_pairs: List[Union[str, Tuple[str, str]]],
-        add_special_tokens: bool = True,
-        padding: Union[bool, str] = False,
-        truncation: Union[bool, str] = False,
-        max_length: Optional[int] = None,
-        stride: int = 0,
-        is_split_into_words: bool = False,
-        pad_to_multiple_of: Optional[int] = None,
-        return_tensors: Optional[Union[str, Any]] = None,
-        return_token_type_ids: Optional[bool] = True,
-        return_attention_mask: Optional[bool] = True,
-        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:
-        all_input_ids = []
-        all_attention_masks = []
-        all_token_type_ids = []
-        all_special_tokens_masks = []
-        all_lengths = []
-
-        for item in batch_text_or_text_pairs:
-            if isinstance(item, tuple):
-                text, text_pair = item
-            else:
-                text, text_pair = item, None
-
-            encoded = self.encode_plus(
-                text=text,
-                text_pair=text_pair,
-                add_special_tokens=add_special_tokens,
-                padding=False,  # We'll handle batch padding later
-                truncation=truncation,
-                max_length=max_length,
-                stride=stride,
-                is_split_into_words=is_split_into_words,
-                pad_to_multiple_of=pad_to_multiple_of,
-                return_tensors=None,  # Don't convert to tensors yet
-                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
-            )
-            
-            all_input_ids.append(encoded["input_ids"])
-            if "attention_mask" in encoded:
-                all_attention_masks.append(encoded["attention_mask"])
-            if "token_type_ids" in encoded:
-                all_token_type_ids.append(encoded["token_type_ids"])
-            if "special_tokens_mask" in encoded:
-                all_special_tokens_masks.append(encoded["special_tokens_mask"])
-            if "length" in encoded:
-                all_lengths.append(encoded["length"])
-
-        batched = {
-            "input_ids": all_input_ids,
-        }
-        
-        if all_attention_masks:
-            batched["attention_mask"] = all_attention_masks
-        if all_token_type_ids:
-            batched["token_type_ids"] = all_token_type_ids
-        if all_special_tokens_masks:
-            batched["special_tokens_mask"] = all_special_tokens_masks
-        if all_lengths:
-            batched["length"] = all_lengths
-
-        # Handle batch padding
-        if padding == True or padding == "longest":
-            max_len = max(len(ids) for ids in all_input_ids)
-            for key in batched:
-                if key in ["input_ids", "attention_mask", "token_type_ids", "special_tokens_mask"]:
-                    padded_seqs = []
-                    for seq in batched[key]:
-                        pad_len = max_len - len(seq)
-                        if pad_len > 0:
-                            if key == "input_ids":
-                                padding_value = self.pad_token_id
-                            else:
-                                padding_value = 0
-                            
-                            if self.padding_side == "right":
-                                padded_seq = seq + [padding_value] * pad_len
-                            else:
-                                padded_seq = [padding_value] * pad_len + seq
-                        else:
-                            padded_seq = seq
-                        padded_seqs.append(padded_seq)
-                    batched[key] = padded_seqs
-
-        if return_tensors == "pt":
-            def to_tensor_list(lst):
-                return [torch.tensor(item, dtype=torch.long) for item in lst]
-            
-            for key in ["input_ids", "attention_mask", "token_type_ids", "special_tokens_mask"]:
-                if key in batched:
-                    batched[key] = torch.nn.utils.rnn.pad_sequence(
-                        to_tensor_list(batched[key]),
-                        batch_first=True,
-                        padding_value=self.pad_token_id if key == "input_ids" else 0
-                    )
-            
-            # Handle non-sequence data
-            if "length" in batched:
-                batched["length"] = torch.tensor(batched["length"], dtype=torch.long)
-
-        return BatchEncoding(batched, tensor_type=return_tensors)
-
-    def save_vocabulary(self, save_directory: str, filename_prefix: Optional[str] = None) -> Tuple[str]:
-        """Save vocabulary to files."""
-        if not os.path.isdir(save_directory):
-            os.makedirs(save_directory)
-            
-        vocab_file = os.path.join(
-            save_directory, 
-            (filename_prefix + "-" if filename_prefix else "") + "vocab.json"
-        )
-        
-        with open(vocab_file, "w", encoding="utf-8") as f:
-            json.dump(self.token_to_id, f, ensure_ascii=False, indent=2)
-        
-        return (vocab_file,)
-
-    def save_pretrained(
-        self, 
-        save_directory: Union[str, os.PathLike],
-        legacy_format: bool = True,
-        filename_prefix: Optional[str] = None,
-        push_to_hub: bool = False,
-        **kwargs
-    ):
-        """Save tokenizer to directory."""
-        if not os.path.exists(save_directory):
-            os.makedirs(save_directory)
-
-        # Save vocabulary
-        vocab_files = self.save_vocabulary(save_directory, filename_prefix)
-        
-        # Save tokenizer config
-        tokenizer_config = {
-            "tokenizer_class": self.__class__.__name__,
-            "model_max_length": self.model_max_length,
-            "padding_side": self.padding_side,
-            "truncation_side": self.truncation_side,
-            "special_tokens": {
-                "bos_token": self.bos_token,
-                "eos_token": self.eos_token,
-                "pad_token": self.pad_token,
-                "unk_token": self.unk_token,
-                "mask_token": self.mask_token,
-            }
-        }
-        
-        config_file = os.path.join(save_directory, "tokenizer_config.json")
-        with open(config_file, "w", encoding="utf-8") as f:
-            json.dump(tokenizer_config, f, ensure_ascii=False, indent=2)
-
-        print(f"✅ Tokenizer saved to: {save_directory}")
-        
-        return (save_directory,)
-
-    @classmethod
-    def from_pretrained(
-        cls, 
-        pretrained_model_name_or_path: Union[str, os.PathLike],
-        *init_inputs,
-        **kwargs
-    ):
-        """Load tokenizer from pretrained directory or hub."""
-        if os.path.isdir(pretrained_model_name_or_path):
-            vocab_file = os.path.join(pretrained_model_name_or_path, "vocab.json")
-            config_file = os.path.join(pretrained_model_name_or_path, "tokenizer_config.json")
-            
-            # Load config if available
-            config = {}
-            if os.path.exists(config_file):
-                with open(config_file, "r", encoding="utf-8") as f:
-                    config = json.load(f)
-            
-            # Merge config with kwargs
-            merged_config = {**config, **kwargs}
-            
-            return cls(vocab_file=vocab_file, **merged_config)
-        else:
-            raise NotImplementedError("Loading from HuggingFace Hub not implemented yet")
-
-    def get_special_tokens_mask(
-        self, 
-        token_ids_0: List[int], 
-        token_ids_1: Optional[List[int]] = None, 
-        already_has_special_tokens: bool = False
-    ) -> List[int]:
-        """Get special tokens mask."""
-        if already_has_special_tokens:
-            return [
-                1 if tid in {self.bos_token_id, self.eos_token_id, self.pad_token_id, self.mask_token_id} 
-                else 0 for tid in token_ids_0
-            ]
-        
-        mask = [1]  # BOS
-        mask.extend([0] * len(token_ids_0))  # Token sequence
-        mask.append(1)  # EOS
-        
-        if token_ids_1 is not None:
-            mask.extend([0] * len(token_ids_1))  # Second sequence
-            mask.append(1)  # EOS
-            
-        return mask
-
-    def create_token_type_ids_from_sequences(
-        self, 
-        token_ids_0: List[int], 
-        token_ids_1: Optional[List[int]] = None
-    ) -> List[int]:
-        """Create token type IDs for sequences."""
-        sep = [self.eos_token_id]
-        cls = [self.bos_token_id]
-        
-        if token_ids_1 is None:
-            return len(cls + token_ids_0 + sep) * [0]
-        
-        return len(cls + token_ids_0 + sep) * [0] + len(token_ids_1 + sep) * [1]
-
-    def build_inputs_with_special_tokens(
-        self, 
-        token_ids_0: List[int], 
-        token_ids_1: Optional[List[int]] = None
-    ) -> List[int]:
-        """Build inputs with special tokens."""
-        if token_ids_1 is None:
-            return [self.bos_token_id] + token_ids_0 + [self.eos_token_id]
-        
-        return ([self.bos_token_id] + token_ids_0 + [self.eos_token_id] + 
-                token_ids_1 + [self.eos_token_id])
-
-
-class FastChemTokenizerSelfies(FastChemTokenizer):
-    """
-    SELFIES variant that handles whitespace-separated tokens.
-    Uses trie-based longest-match encoding (same as original working version).
-    """
-
-    def _encode_core(self, text: str) -> List[int]:
-        """Trie-based encoding for SELFIES with fragment + atom vocab."""
-        result_ids = []
-        i = 0
-        n = len(text)
-
-        while i < n:
-            if text[i].isspace():  # skip literal whitespace
-                i += 1
-                continue
-
-            node = self.trie_root
-            j = i
-            last_match_id = None
-            last_match_end = i
-
-            # Traverse trie character by character (including spaces if part of vocab key)
-            while j < n and text[j] in node.children:
-                node = node.children[text[j]]
-                j += 1
-                if node.token_id is not None:
-                    last_match_id = node.token_id
-                    last_match_end = j
-
-            if last_match_id is not None:
-                result_ids.append(last_match_id)
-                i = last_match_end
-            else:
-                # Fallback: encode one char as unk or atom
-                result_ids.append(self.token_to_id.get(text[i], self.unk_token_id))
-                i += 1
-
-        return result_ids
-
-    def convert_tokens_to_string(self, tokens: List[str]) -> str:
-        """SELFIES decoding: join tokens with spaces (preserve original format)."""
-        return " ".join(tokens)
-
-    def decode(
-        self,
-        token_ids: Union[List[int], torch.Tensor],
-        skip_special_tokens: bool = False,
-        clean_up_tokenization_spaces: bool = None,
-        **kwargs
-    ) -> str:
-        if isinstance(token_ids, torch.Tensor):
-            token_ids = token_ids.tolist()
-
-        if skip_special_tokens:
-            special_ids = {
-                self.bos_token_id,
-                self.eos_token_id,
-                self.pad_token_id,
-                self.mask_token_id,
-            }
-        else:
-            special_ids = set()
-
-        tokens = []
-        for tid in token_ids:
-            if tid in special_ids:
-                continue
-            token = self.id_to_token.get(tid, self.unk_token)
-            tokens.append(token)
-
-        return " ".join(tokens)   # ✅ preserve spaces        return " ".join(tokens)   # ✅ preserve spaces
+import torch
+import json
+import os
+from typing import List, Union, Optional, Tuple, Dict, Any
+from functools import lru_cache
+from collections.abc import Mapping
+
+
+# ------------------------------
+# BatchEncoding
+# ------------------------------
+class BatchEncoding(dict, Mapping):
+    """Minimal BatchEncoding compatible wrapper."""
+
+    def __init__(self, data: dict, tensor_type: Optional[str] = None):
+        data = {} if data is None else {k: v for k, v in data.items()}
+        super().__init__(data)
+        self.data = data
+        self.tensor_type = tensor_type
+        for k, v in data.items():
+            setattr(self, k, v)
+
+    def __getitem__(self, key): return self.data[key]
+    def __iter__(self): return iter(self.data)
+    def __len__(self): return len(self.data)
+    def keys(self): return self.data.keys()
+    def values(self): return self.data.values()
+    def items(self): return self.data.items()
+    def get(self, key, default=None): return self.data.get(key, default)
+
+    def to(self, device):
+        if self.tensor_type in ("pt", "torch"):
+            for k, v in list(self.data.items()):
+                if torch.is_tensor(v):
+                    self.data[k] = v.to(device)
+                    setattr(self, k, self.data[k])
+        return self
+
+    def cpu(self): return self.to("cpu")
+    def cuda(self): return self.to("cuda")
+    def detach(self):
+        if self.tensor_type in ("pt", "torch"):
+            for k, v in list(self.data.items()):
+                if torch.is_tensor(v):
+                    self.data[k] = v.detach()
+                    setattr(self, k, self.data[k])
+        return self
+
+    def __repr__(self):
+        keys = ", ".join(list(self.data.keys())[:10])
+        return f"BatchEncoding(keys=[{keys}], tensor_type={self.tensor_type})"
+
+
+# ------------------------------
+# Base class
+# ------------------------------
+class PreTrainedTokenizerBase:
+    def __init__(self, **kwargs):
+        for key, value in kwargs.items():
+            if key.endswith('_token'):
+                setattr(self, f"_{key}", value)
+                setattr(self, f"{key}_id", None)
+        self.model_max_length = kwargs.get('model_max_length', 512)
+        self.padding_side = kwargs.get('padding_side', 'right')
+        self.truncation_side = kwargs.get('truncation_side', 'right')
+        self.chat_template = kwargs.get('chat_template')
+
+
+# ------------------------------
+# Trie node
+# ------------------------------
+class TrieNode:
+    __slots__ = ['children', 'token_id']
+    def __init__(self):
+        self.children = {}
+        self.token_id = None
+
+
+# ------------------------------
+# FastChemTokenizer
+# ------------------------------
+
+class FastChemTokenizer(PreTrainedTokenizerBase):
+    def __init__(self, token_to_id=None, vocab_file=None, **kwargs):
+        if vocab_file is not None:
+            with open(vocab_file, "r", encoding="utf-8") as f:
+                token_to_id = json.load(f)
+                token_to_id = {str(k): int(v) for k, v in token_to_id.items()}
+
+        self.token_to_id = token_to_id
+        self.id_to_token = {v: k for k, v in token_to_id.items()}
+
+        # Build trie
+        self.trie_root = self._build_trie(self.token_to_id)
+
+        # ✅ Call parent (sets token *strings*, may reset *_id to None)
+        super().__init__(
+            bos_token="<s>",
+            eos_token="</s>",
+            unk_token="<unk>",
+            pad_token="<pad>",
+            mask_token="<mask>",
+            model_max_length=kwargs.get("model_max_length", 512),
+            padding_side=kwargs.get("padding_side", "right"),
+            truncation_side=kwargs.get("truncation_side", "right"),
+            **kwargs,
+        )
+
+        # ✅ Re-map token strings → IDs from vocab
+        self.bos_token_id  = self.token_to_id.get("<s>", 0)
+        self.eos_token_id  = self.token_to_id.get("</s>", 1)
+        self.pad_token_id  = self.token_to_id.get("<pad>", 2)
+        self.unk_token_id  = self.token_to_id.get("<unk>", 3)
+        self.mask_token_id = self.token_to_id.get("<mask>", 4)
+
+        # Ensure reverse mapping always valid
+        self.id_to_token[self.bos_token_id]  = "<s>"
+        self.id_to_token[self.eos_token_id]  = "</s>"
+        self.id_to_token[self.pad_token_id]  = "<pad>"
+        self.id_to_token[self.unk_token_id]  = "<unk>"
+        self.id_to_token[self.mask_token_id] = "<mask>"
+
+        # Debug
+        print("✅ Special tokens bound:",
+              self.bos_token_id, self.eos_token_id, self.pad_token_id,
+              self.unk_token_id, self.mask_token_id)
+        
+        # ✅ Ensure token *strings* also exist (for decode fallback)
+        self.bos_token = "<s>"
+        self.eos_token = "</s>"
+        self.pad_token = "<pad>"
+        self.unk_token = "<unk>"
+        self.mask_token = "<mask>"
+
+
+    def _build_trie(self, token_to_id):
+        root = TrieNode()
+        for token, tid in token_to_id.items():
+            node = root
+            for char in token:
+                if char not in node.children:
+                    node.children[char] = TrieNode()
+                node = node.children[char]
+            node.token_id = tid
+        return root
+
+    @property
+    def vocab_size(self): return len(self.token_to_id)
+    def __len__(self): return len(self.token_to_id)
+    def get_vocab(self) -> Dict[str, int]: return self.token_to_id.copy()
+
+    @lru_cache(maxsize=10000)
+    def _cached_encode_str(self, s: str) -> Tuple[int, ...]:
+        return tuple(self._encode_core(s))
+
+    def _encode_core(self, text: str) -> List[int]:
+        tokens, result_ids = text, []
+        i, n = 0, len(tokens)
+        while i < n:
+            node, j = self.trie_root, i
+            last_match_id, last_match_end = None, i
+            while j < n and tokens[j] in node.children:
+                node = node.children[tokens[j]]
+                j += 1
+                if node.token_id is not None:
+                    last_match_id, last_match_end = node.token_id, j
+            if last_match_id is not None:
+                result_ids.append(last_match_id)
+                i = last_match_end
+            else:
+                tid = self.token_to_id.get(tokens[i], self.unk_token_id)
+                result_ids.append(tid)
+                i += 1
+        return result_ids
+
+    # ------------------------------
+    # Converters
+    # ------------------------------
+    def _convert_token_to_id(self, token: str) -> int:
+        return self.token_to_id.get(token, self.unk_token_id)
+    def _convert_id_to_token(self, index: int) -> str:
+        return self.id_to_token.get(index, self.unk_token)
+
+    def convert_tokens_to_ids(self, tokens: Union[str, List[str]]):
+        if isinstance(tokens, str): return self._convert_token_to_id(tokens)
+        return [self._convert_token_to_id(tok) for tok in tokens]
+
+    def convert_ids_to_tokens(self, ids: Union[int, List[int]]):
+        if isinstance(ids, int): return self._convert_id_to_token(ids)
+        return [self._convert_id_to_token(i) for i in ids]
+
+    def convert_tokens_to_string(self, tokens: List[str]) -> str: return "".join(tokens)
+
+    # ------------------------------
+    # Encoding / Decoding
+    # ------------------------------
+        # ------------------------------
+    # Convenience wrappers
+    # ------------------------------
+    def encode(
+        self,
+        text: str,
+        text_pair: Optional[str] = None,
+        add_special_tokens: bool = True,
+        padding: bool = False,
+        truncation: bool = False,
+        max_length: Optional[int] = None,
+        return_tensors: Optional[str] = None,
+    ) -> List[int]:
+        encoded = self.encode_plus(
+            text=text,
+            text_pair=text_pair,
+            add_special_tokens=add_special_tokens,
+            padding=padding,
+            truncation=truncation,
+            max_length=max_length,
+            return_tensors=return_tensors,
+        )
+        input_ids = encoded["input_ids"]
+        if isinstance(input_ids, torch.Tensor):
+            if input_ids.dim() > 1:
+                input_ids = input_ids.squeeze(0)
+            input_ids = input_ids.tolist()
+        return input_ids
+
+    def __call__(
+        self, 
+        text: Union[str, List[str]], 
+        text_pair: Optional[Union[str, List[str]]] = 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_split_into_words: bool = False,
+        pad_to_multiple_of: Optional[int] = None,
+        return_tensors: Optional[Union[str, Any]] = 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:
+        """HuggingFace-compatible: one string → encode_plus, list → batch_encode_plus"""
+        if return_token_type_ids is None:
+            return_token_type_ids = True
+        if return_attention_mask is None:
+            return_attention_mask = True
+
+        if isinstance(text, list):
+            if text_pair is not None:
+                batch = [(t, p) for t, p in zip(text, text_pair)]
+            else:
+                batch = text
+            return self.batch_encode_plus(
+                batch,
+                add_special_tokens=add_special_tokens,
+                padding=padding,
+                truncation=truncation,
+                max_length=max_length,
+                stride=stride,
+                is_split_into_words=is_split_into_words,
+                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_split_into_words=is_split_into_words,
+                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: str,
+        text_pair: Optional[str] = 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_split_into_words: bool = False,
+        pad_to_multiple_of: Optional[int] = None,
+        return_tensors: Optional[Union[str, Any]] = None,
+        return_token_type_ids: Optional[bool] = True,
+        return_attention_mask: Optional[bool] = True,
+        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:
+        if max_length is None: max_length = self.model_max_length
+        ids_a = list(self._cached_encode_str(text.strip()))
+        ids_b = list(self._cached_encode_str(text_pair.strip())) if text_pair else None
+
+        input_ids, token_type_ids = [], []
+        if add_special_tokens:
+            input_ids.append(self.bos_token_id); token_type_ids.append(0)
+            input_ids.extend(ids_a); token_type_ids.extend([0] * len(ids_a))
+            input_ids.append(self.eos_token_id); token_type_ids.append(0)
+            if ids_b is not None:
+                input_ids.extend(ids_b); token_type_ids.extend([1] * len(ids_b))
+                input_ids.append(self.eos_token_id); token_type_ids.append(1)
+        else:
+            input_ids = ids_a.copy(); token_type_ids = [0] * len(input_ids)
+            if ids_b is not None:
+                input_ids.extend(ids_b); token_type_ids.extend([1] * len(ids_b))
+
+        if truncation and len(input_ids) > max_length:
+            input_ids, token_type_ids = input_ids[:max_length], token_type_ids[:max_length]
+
+        encoded_dict = {"input_ids": input_ids}
+        if return_attention_mask:
+            if padding == True or padding == "max_length":
+                pad_len = max_length - len(input_ids)
+                if pad_len > 0:
+                    if self.padding_side == "right":
+                        input_ids.extend([self.pad_token_id] * pad_len)
+                        token_type_ids.extend([0] * pad_len)
+                    else:
+                        input_ids = [self.pad_token_id] * pad_len + input_ids
+                        token_type_ids = [0] * pad_len + token_type_ids
+            attention_mask = [0 if tid == self.pad_token_id else 1 for tid in input_ids]
+            encoded_dict["attention_mask"] = attention_mask
+        if return_token_type_ids: encoded_dict["token_type_ids"] = token_type_ids
+        if return_special_tokens_mask:
+            encoded_dict["special_tokens_mask"] = [
+                1 if tid in {self.bos_token_id, self.eos_token_id, self.pad_token_id, self.mask_token_id} else 0
+                for tid in input_ids
+            ]
+        if return_length:
+            encoded_dict["length"] = len([tid for tid in input_ids if tid != self.pad_token_id])
+
+        if return_tensors in ["pt", "torch"]:
+            out = {}
+            for k, v in encoded_dict.items():
+                if isinstance(v, list):
+                    tensor = torch.tensor(
+                        [self.unk_token_id if x is None else int(x) for x in v], dtype=torch.long
+                    ).unsqueeze(0)
+                    out[k] = tensor
+                else:
+                    out[k] = v
+            return BatchEncoding(out, tensor_type=return_tensors)
+        return BatchEncoding(encoded_dict, tensor_type=None)
+
+    def batch_encode_plus(
+        self,
+        batch_text_or_text_pairs: List[Union[str, Tuple[str, str]]],
+        add_special_tokens: bool = True,
+        padding: Union[bool, str] = False,
+        truncation: Union[bool, str] = False,
+        max_length: Optional[int] = None,
+        stride: int = 0,
+        is_split_into_words: bool = False,
+        pad_to_multiple_of: Optional[int] = None,
+        return_tensors: Optional[Union[str, Any]] = None,
+        return_token_type_ids: Optional[bool] = True,
+        return_attention_mask: Optional[bool] = True,
+        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:
+        if padding is True: padding = "longest"
+        if padding == "max_length" and max_length is None: max_length = self.model_max_length
+
+        all_input_ids, all_token_type_ids, all_attention_masks = [], [], []
+        all_special_masks, all_lengths = [], []
+        for item in batch_text_or_text_pairs:
+            t, tp = item if isinstance(item, tuple) else (item, None)
+            enc = self.encode_plus(
+                text=t, text_pair=tp, add_special_tokens=add_special_tokens,
+                padding=False, truncation=truncation, max_length=max_length,
+                return_tensors=None, return_token_type_ids=return_token_type_ids,
+                return_attention_mask=return_attention_mask,
+                return_special_tokens_mask=return_special_tokens_mask,
+                return_length=return_length, **kwargs
+            )
+            ids, tt, am = enc["input_ids"], enc.get("token_type_ids", [0]*len(enc["input_ids"])), enc.get("attention_mask",[1]*len(enc["input_ids"]))
+            sm, ln = enc.get("special_tokens_mask",[0]*len(ids)), enc.get("length", len([x for x in ids if x != self.pad_token_id]))
+            all_input_ids.append(ids); all_token_type_ids.append(tt); all_attention_masks.append(am)
+            all_special_masks.append(sm); all_lengths.append(ln)
+
+        pad_to = max(len(x) for x in all_input_ids) if padding == "longest" else (max_length if padding == "max_length" else None)
+        batched = {
+            "input_ids": all_input_ids,
+            "token_type_ids": all_token_type_ids if return_token_type_ids else None,
+            "attention_mask": all_attention_masks if return_attention_mask else None,
+            "special_tokens_mask": all_special_masks if return_special_tokens_mask else None,
+            "length": all_lengths if return_length else None,
+        }
+        if pad_to is not None:
+            for key in ["input_ids","token_type_ids","attention_mask","special_tokens_mask"]:
+                if batched.get(key) is None: continue
+                padded = []
+                for seq in batched[key]:
+                    pad_len = pad_to - len(seq)
+                    pad_val = self.pad_token_id if key=="input_ids" else 0
+                    if pad_len > 0:
+                        seq = seq+[pad_val]*pad_len if self.padding_side=="right" else [pad_val]*pad_len+seq
+                    padded.append(seq)
+                batched[key] = padded
+
+        if return_tensors in ["pt", "torch"]:
+            def to_tensor(lst, pad_val=0):
+                return torch.tensor([[self.unk_token_id if x is None else int(x) for x in row] for row in lst], dtype=torch.long)
+            out = {}
+            if batched.get("input_ids") is not None: out["input_ids"] = to_tensor(batched["input_ids"], self.pad_token_id)
+            if batched.get("attention_mask") is not None: out["attention_mask"] = to_tensor(batched["attention_mask"],0)
+            if batched.get("token_type_ids") is not None: out["token_type_ids"] = to_tensor(batched["token_type_ids"],0)
+            if batched.get("special_tokens_mask") is not None: out["special_tokens_mask"] = to_tensor(batched["special_tokens_mask"],0)
+            if return_length and batched.get("length") is not None: out["length"] = torch.tensor([int(x) for x in batched["length"]], dtype=torch.long)
+            return BatchEncoding(out, tensor_type=return_tensors)
+        return BatchEncoding({k:v for k,v in batched.items() if v is not None}, tensor_type=None)
+
+    # ------------------------------
+    # Decoding
+    # ------------------------------
+    def decode(self, token_ids, skip_special_tokens=False, **kwargs):
+        if isinstance(token_ids, torch.Tensor): token_ids = token_ids.tolist()
+        special_ids = {self.bos_token_id,self.eos_token_id,self.pad_token_id,self.mask_token_id} if skip_special_tokens else set()
+        tokens = [self.id_to_token.get(tid,self.unk_token) for tid in token_ids if tid not in special_ids]
+        return "".join(tokens)
+
+    def batch_decode(self, sequences, skip_special_tokens=False, **kwargs):
+        if isinstance(sequences, torch.Tensor): sequences = sequences.tolist()
+        return [self.decode(seq, skip_special_tokens=skip_special_tokens, **kwargs) for seq in sequences]
+
+    def decode_with_trace(self, token_ids: List[int]):
+        print(f"\n🔍 Decoding {len(token_ids)} tokens:")
+        for i, tid in enumerate(token_ids):
+            token = self.id_to_token.get(tid, self.unk_token)
+            tid_str = "None" if tid is None else f"{tid:5d}"
+            print(f"  [{i:03d}] ID={tid_str} → '{token}'")
+    
+    def pad(
+        self,
+        encoded_inputs,
+        padding=True,
+        max_length=None,
+        pad_to_multiple_of=None,
+        return_tensors=None,
+        **kwargs,
+    ):
+        """
+        HuggingFace-style pad. Takes a list/dict of encoded inputs and pads them.
+        """
+        if isinstance(encoded_inputs, dict):
+            encoded_inputs = [encoded_inputs]
+
+        input_ids = [ei["input_ids"] for ei in encoded_inputs]
+        attn_masks = [ei.get("attention_mask", [1]*len(ei["input_ids"])) for ei in encoded_inputs]
+
+        # determine pad length
+        max_len = max(len(ids) for ids in input_ids)
+        if pad_to_multiple_of:
+            max_len = ((max_len + pad_to_multiple_of - 1) // pad_to_multiple_of) * pad_to_multiple_of
+        if max_length is not None:
+            max_len = min(max_len, max_length)
+
+        padded_ids, padded_masks = [], []
+        for ids, mask in zip(input_ids, attn_masks):
+            pad_len = max_len - len(ids)
+            if self.padding_side == "right":
+                padded_ids.append(ids + [self.pad_token_id] * pad_len)
+                padded_masks.append(mask + [0] * pad_len)
+            else:
+                padded_ids.append([self.pad_token_id] * pad_len + ids)
+                padded_masks.append([0] * pad_len + mask)
+
+        out = {"input_ids": padded_ids, "attention_mask": padded_masks}
+        if return_tensors in ["pt", "torch"]:
+            out = {k: torch.tensor(v, dtype=torch.long) for k, v in out.items()}
+        return out
+
+
+    # ------------------------------
+    # Save / Load
+    # ------------------------------
+    def save_vocabulary(self, save_directory: str, filename_prefix: Optional[str] = None) -> Tuple[str]:
+        if not os.path.isdir(save_directory): os.makedirs(save_directory)
+        vocab_file = os.path.join(save_directory,(filename_prefix+"-" if filename_prefix else "")+"vocab.json")
+        with open(vocab_file,"w",encoding="utf-8") as f: json.dump(self.token_to_id,f,ensure_ascii=False,indent=2)
+        return (vocab_file,)
+
+    def save_pretrained(self, save_directory: Union[str, os.PathLike], filename_prefix: Optional[str]=None, **kwargs):
+        if not os.path.exists(save_directory): os.makedirs(save_directory)
+        self.save_vocabulary(save_directory, filename_prefix)
+        config_file = os.path.join(save_directory,"tokenizer_config.json")
+        with open(config_file,"w",encoding="utf-8") as f:
+            json.dump({
+                "tokenizer_class": self.__class__.__name__,
+                "model_max_length": self.model_max_length,
+                "padding_side": self.padding_side,
+                "truncation_side": self.truncation_side,
+                "special_tokens": {
+                    "bos_token": self.bos_token,
+                    "eos_token": self.eos_token,
+                    "pad_token": self.pad_token,
+                    "unk_token": self.unk_token,
+                    "mask_token": self.mask_token,
+                }
+            },f,ensure_ascii=False,indent=2)
+        return (save_directory,)
+
+    @classmethod
+    def from_pretrained(cls, pretrained_model_name_or_path, **kwargs):
+        if os.path.isdir(pretrained_model_name_or_path):
+            vocab_file = os.path.join(pretrained_model_name_or_path,"vocab.json")
+            config_file = os.path.join(pretrained_model_name_or_path,"tokenizer_config.json")
+            config = {}
+            if os.path.exists(config_file):
+                with open(config_file,"r",encoding="utf-8") as f: config=json.load(f)
+            return cls(vocab_file=vocab_file, **{**config,**kwargs})
+        else:
+            raise NotImplementedError("Loading from Hub not implemented yet")
+
+
+# ------------------------------
+# SELFIES variant
+# ------------------------------
+class FastChemTokenizerSelfies(FastChemTokenizer):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)  # ✅ ensures BOS/EOS etc. are set
+
+    """SELFIES variant that handles whitespace-separated tokens."""
+
+    def _encode_core(self, text: str) -> List[int]:
+        result_ids, i, n = [], 0, len(text)
+        while i < n:
+            if text[i].isspace(): i += 1; continue
+            node, j = self.trie_root, i
+            last_match_id, last_match_end = None, i
+            while j < n and text[j] in node.children:
+                node = node.children[text[j]]; j += 1
+                if node.token_id is not None:
+                    last_match_id, last_match_end = node.token_id, j
+            if last_match_id is not None:
+                result_ids.append(last_match_id); i = last_match_end
+            else:
+                result_ids.append(self.token_to_id.get(text[i], self.unk_token_id)); i += 1
+        return result_ids
+
+    def convert_tokens_to_string(self, tokens: List[str]) -> str: return " ".join(tokens)
+    def decode(self, token_ids, skip_special_tokens=False, **kwargs):
+        if isinstance(token_ids, torch.Tensor): token_ids = token_ids.tolist()
+        special_ids = {self.bos_token_id,self.eos_token_id,self.pad_token_id,self.mask_token_id} if skip_special_tokens else set()
+        tokens = [self.id_to_token.get(tid,self.unk_token) for tid in token_ids if tid not in special_ids]
+        return " ".join(tokens)