model_without_OpenMMLab/segformer_plusplus/configs/config/config.py

import ast
import copy
import os
import os.path as osp
import platform
import shutil
import sys
import tempfile
import types
import uuid
import re
import warnings
from argparse import ArgumentParser
from collections import OrderedDict, abc
from pathlib import Path
from typing import Any, Optional, Tuple, Union
from omegaconf import OmegaConf
import yapf
from addict import Dict
from yapf.yapflib.yapf_api import FormatCode

from .lazy import LazyAttr, LazyObject
from .utils import (check_file_exist, get_installed_path, import_modules_from_strings, is_installed, RemoveAssignFromAST, 
                    ImportTransformer, _gather_abs_import_lazyobj, _get_external_cfg_base_path,
                    _get_external_cfg_path, _get_package_and_cfg_path, _is_builtin_module, dump)


BASE_KEY = '_base_'
DELETE_KEY = '_delete_'
DEPRECATION_KEY = '_deprecation_'
RESERVED_KEYS = ['filename', 'text', 'pretty_text', 'env_variables']


def _lazy2string(cfg_dict, dict_type=None):
    if isinstance(cfg_dict, dict):
        dict_type = dict_type or type(cfg_dict)
        return dict_type(
            {k: _lazy2string(v, dict_type)
             for k, v in dict.items(cfg_dict)})
    elif isinstance(cfg_dict, (tuple, list)):
        return type(cfg_dict)(_lazy2string(v, dict_type) for v in cfg_dict)
    elif isinstance(cfg_dict, (LazyAttr, LazyObject)):
        return f'{cfg_dict.module}.{str(cfg_dict)}'
    else:
        return cfg_dict


class ConfigDict(Dict):
    """A dictionary for config which has the same interface as python's built-
    in dictionary and can be used as a normal dictionary.

    The Config class would transform the nested fields (dictionary-like fields)
    in config file into ``ConfigDict``.

    If the class attribute ``lazy``  is ``False``, users will get the
    object built by ``LazyObject`` or ``LazyAttr``, otherwise users will get
    the ``LazyObject`` or ``LazyAttr`` itself.

    The ``lazy`` should be set to ``True`` to avoid building the imported
    object during configuration parsing, and it should be set to False outside
    the Config to ensure that users do not experience the ``LazyObject``.
    """
    lazy = False

    def __init__(__self, *args, **kwargs):
        object.__setattr__(__self, '__parent', kwargs.pop('__parent', None))
        object.__setattr__(__self, '__key', kwargs.pop('__key', None))
        object.__setattr__(__self, '__frozen', False)
        for arg in args:
            if not arg:
                continue
            # Since ConfigDict.items will convert LazyObject to real object
            # automatically, we need to call super().items() to make sure
            # the LazyObject will not be converted.
            if isinstance(arg, ConfigDict):
                for key, val in dict.items(arg):
                    __self[key] = __self._hook(val)
            elif isinstance(arg, dict):
                for key, val in arg.items():
                    __self[key] = __self._hook(val)
            elif isinstance(arg, tuple) and (not isinstance(arg[0], tuple)):
                __self[arg[0]] = __self._hook(arg[1])
            else:
                for key, val in iter(arg):
                    __self[key] = __self._hook(val)

        for key, val in dict.items(kwargs):
            __self[key] = __self._hook(val)

    def __missing__(self, name):
        raise KeyError(name)

    def __getattr__(self, name):
        try:
            value = super().__getattr__(name)
            if isinstance(value, (LazyAttr, LazyObject)) and not self.lazy:
                value = value.build()
        except KeyError:
            raise AttributeError(f"'{self.__class__.__name__}' object has no "
                                 f"attribute '{name}'")
        except Exception as e:
            raise e
        else:
            return value

    @classmethod
    def _hook(cls, item):
        # avoid to convert user defined dict to ConfigDict.
        if type(item) in (dict, OrderedDict):
            return cls(item)
        elif isinstance(item, (list, tuple)):
            return type(item)(cls._hook(elem) for elem in item)
        return item

    def __setattr__(self, name, value):
        value = self._hook(value)
        return super().__setattr__(name, value)

    def __setitem__(self, name, value):
        value = self._hook(value)
        return super().__setitem__(name, value)

    def __getitem__(self, key):
        return self.build_lazy(super().__getitem__(key))

    def __deepcopy__(self, memo):
        other = self.__class__()
        memo[id(self)] = other
        for key, value in super().items():
            other[copy.deepcopy(key, memo)] = copy.deepcopy(value, memo)
        return other

    def __copy__(self):
        other = self.__class__()
        for key, value in super().items():
            other[key] = value
        return other

    copy = __copy__

    def __iter__(self):
        # Implement `__iter__` to overwrite the unpacking operator `**cfg_dict`
        # to get the built lazy object
        return iter(self.keys())

    def get(self, key: str, default: Optional[Any] = None) -> Any:
        """Get the value of the key. If class attribute ``lazy`` is True, the
        LazyObject will be built and returned.

        Args:
            key (str): The key.
            default (any, optional): The default value. Defaults to None.

        Returns:
            Any: The value of the key.
        """
        return self.build_lazy(super().get(key, default))

    def pop(self, key, default=None):
        """Pop the value of the key. If class attribute ``lazy`` is True, the
        LazyObject will be built and returned.

        Args:
            key (str): The key.
            default (any, optional): The default value. Defaults to None.

        Returns:
            Any: The value of the key.
        """
        return self.build_lazy(super().pop(key, default))

    def update(self, *args, **kwargs) -> None:
        """Override this method to make sure the LazyObject will not be built
        during updating."""
        other = {}
        if args:
            if len(args) > 1:
                raise TypeError('update only accept one positional argument')
            # Avoid to used self.items to build LazyObject
            for key, value in dict.items(args[0]):
                other[key] = value

        for key, value in dict(kwargs).items():
            other[key] = value
        for k, v in other.items():
            if ((k not in self) or (not isinstance(self[k], dict))
                    or (not isinstance(v, dict))):
                self[k] = self._hook(v)
            else:
                self[k].update(v)

    def build_lazy(self, value: Any) -> Any:
        """If class attribute ``lazy`` is False, the LazyObject will be built
        and returned.

        Args:
            value (Any): The value to be built.

        Returns:
            Any: The built value.
        """
        if isinstance(value, (LazyAttr, LazyObject)) and not self.lazy:
            value = value.build()
        return value

    def values(self):
        """Yield the values of the dictionary.

        If class attribute ``lazy`` is False, the value of ``LazyObject`` or
        ``LazyAttr`` will be built and returned.
        """
        values = []
        for value in super().values():
            values.append(self.build_lazy(value))
        return values

    def items(self):
        """Yield the keys and values of the dictionary.

        If class attribute ``lazy`` is False, the value of ``LazyObject`` or
        ``LazyAttr`` will be built and returned.
        """
        items = []
        for key, value in super().items():
            items.append((key, self.build_lazy(value)))
        return items

    def merge(self, other: dict):
        """Merge another dictionary into current dictionary.

        Args:
            other (dict): Another dictionary.
        """
        default = object()

        def _merge_a_into_b(a, b):
            if isinstance(a, dict):
                if not isinstance(b, dict):
                    a.pop(DELETE_KEY, None)
                    return a
                if a.pop(DELETE_KEY, False):
                    b.clear()
                all_keys = list(b.keys()) + list(a.keys())
                return {
                    key:
                    _merge_a_into_b(a.get(key, default), b.get(key, default))
                    for key in all_keys if key != DELETE_KEY
                }
            else:
                return a if a is not default else b

        merged = _merge_a_into_b(copy.deepcopy(other), copy.deepcopy(self))
        self.clear()
        for key, value in merged.items():
            self[key] = value

    def __reduce_ex__(self):
        # Override __reduce_ex__ to avoid `self.items` will be
        # called by CPython interpreter during pickling. See more details in
        # https://github.com/python/cpython/blob/8d61a71f9c81619e34d4a30b625922ebc83c561b/Objects/typeobject.c#L6196  # noqa: E501
        from ...utils import digit_version
        if digit_version(platform.python_version()) < digit_version('3.8'):
            return (self.__class__, ({k: v
                                      for k, v in super().items()}, ), None,
                    None, None)
        else:
            return (self.__class__, ({k: v
                                      for k, v in super().items()}, ), None,
                    None, None, None)

    def __eq__(self, other):
        if isinstance(other, ConfigDict):
            return other.to_dict() == self.to_dict()
        elif isinstance(other, dict):
            return {k: v for k, v in self.items()} == other
        else:
            return False

    def _to_lazy_dict(self):
        """Convert the ConfigDict to a normal dictionary recursively, and keep
        the ``LazyObject`` or ``LazyAttr`` object not built."""

        def _to_dict(data):
            if isinstance(data, ConfigDict):
                return {
                    key: _to_dict(value)
                    for key, value in Dict.items(data)
                }
            elif isinstance(data, dict):
                return {key: _to_dict(value) for key, value in data.items()}
            elif isinstance(data, (list, tuple)):
                return type(data)(_to_dict(item) for item in data)
            else:
                return data

        return _to_dict(self)

    def to_dict(self):
        """Convert the ConfigDict to a normal dictionary recursively, and
        convert the ``LazyObject`` or ``LazyAttr`` to string."""
        return _lazy2string(self, dict_type=dict)


def add_args(parser: ArgumentParser,
             cfg: dict,
             prefix: str = '') -> ArgumentParser:
    """Add config fields into argument parser.

    Args:
        parser (ArgumentParser): Argument parser.
        cfg (dict): Config dictionary.
        prefix (str, optional): Prefix of parser argument.
            Defaults to ''.

    Returns:
        ArgumentParser: Argument parser containing config fields.
    """
    for k, v in cfg.items():
        if isinstance(v, str):
            parser.add_argument('--' + prefix + k)
        elif isinstance(v, bool):
            parser.add_argument('--' + prefix + k, action='store_true')
        elif isinstance(v, int):
            parser.add_argument('--' + prefix + k, type=int)
        elif isinstance(v, float):
            parser.add_argument('--' + prefix + k, type=float)
        elif isinstance(v, dict):
            add_args(parser, v, prefix + k + '.')
        elif isinstance(v, abc.Iterable):
            parser.add_argument(
                '--' + prefix + k, type=type(next(iter(v))), nargs='+')
    return parser


class Config:
    """A facility for config and config files.

    It supports common file formats as configs: python/json/yaml.
    ``Config.fromfile`` can parse a dictionary from a config file, then
    build a ``Config`` instance with the dictionary.
    The interface is the same as a dict object and also allows access config
    values as attributes.

    Args:
        cfg_dict (dict, optional): A config dictionary. Defaults to None.
        cfg_text (str, optional): Text of config. Defaults to None.
        filename (str or Path, optional): Name of config file.
            Defaults to None.
        format_python_code (bool): Whether to format Python code by yapf.
            Defaults to True.
    """  # noqa: E501

    def __init__(
        self,
        cfg_dict: Optional[dict] = None,
        cfg_text: Optional[str] = None,
        filename: Optional[Union[str, Path]] = None,
        env_variables: Optional[dict] = None,
        format_python_code: bool = True,
    ):
        filename = str(filename) if isinstance(filename, Path) else filename
        if cfg_dict is None:
            cfg_dict = dict()
        elif not isinstance(cfg_dict, dict):
            raise TypeError('cfg_dict must be a dict, but '
                            f'got {type(cfg_dict)}')
        for key in cfg_dict:
            if key in RESERVED_KEYS:
                raise KeyError(f'{key} is reserved for config file')

        if not isinstance(cfg_dict, ConfigDict):
            cfg_dict = ConfigDict(cfg_dict)
        super().__setattr__('_cfg_dict', cfg_dict)
        super().__setattr__('_filename', filename)
        super().__setattr__('_format_python_code', format_python_code)
        if not hasattr(self, '_imported_names'):
            super().__setattr__('_imported_names', set())

        if cfg_text:
            text = cfg_text
        elif filename:
            with open(filename, encoding='utf-8') as f:
                text = f.read()
        else:
            text = ''
        super().__setattr__('_text', text)
        if env_variables is None:
            env_variables = dict()
        super().__setattr__('_env_variables', env_variables)

    @staticmethod
    def fromfile(filename: Union[str, Path],
                 use_predefined_variables: bool = True,
                 import_custom_modules: bool = True,
                 use_environment_variables: bool = True,
                 lazy_import: Optional[bool] = None,
                 format_python_code: bool = True) -> 'Config':
        """Build a Config instance from config file.

        Args:
            filename (str or Path): Name of config file.
            use_predefined_variables (bool, optional): Whether to use
                predefined variables. Defaults to True.
            import_custom_modules (bool, optional): Whether to support
                importing custom modules in config. Defaults to None.
            use_environment_variables (bool, optional): Whether to use
                environment variables. Defaults to True.
            lazy_import (bool): Whether to load config in `lazy_import` mode.
                If it is `None`, it will be deduced by the content of the
                config file. Defaults to None.
            format_python_code (bool): Whether to format Python code by yapf.
                Defaults to True.

        Returns:
            Config: Config instance built from config file.
        """
        filename = str(filename) if isinstance(filename, Path) else filename
        if lazy_import is False or \
           lazy_import is None and not Config._is_lazy_import(filename):
            cfg_dict, cfg_text, env_variables = Config._file2dict(
                filename, use_predefined_variables, use_environment_variables,
                lazy_import)
            if import_custom_modules and cfg_dict.get('custom_imports', None):
                try:
                    import_modules_from_strings(**cfg_dict['custom_imports'])
                except ImportError as e:
                    err_msg = (
                        'Failed to import custom modules from '
                        f"{cfg_dict['custom_imports']}, the current sys.path "
                        'is: ')
                    for p in sys.path:
                        err_msg += f'\n    {p}'
                    err_msg += (
                        '\nYou should set `PYTHONPATH` to make `sys.path` '
                        'include the directory which contains your custom '
                        'module')
                    raise ImportError(err_msg) from e
            return Config(
                cfg_dict,
                cfg_text=cfg_text,
                filename=filename,
                env_variables=env_variables,
            )
        else:
            # Enable lazy import when parsing the config.
            # Using try-except to make sure ``ConfigDict.lazy`` will be reset
            # to False. See more details about lazy in the docstring of
            # ConfigDict
            ConfigDict.lazy = True
            try:
                cfg_dict, imported_names = Config._parse_lazy_import(filename)
            except Exception as e:
                raise e
            finally:
                # disable lazy import to get the real type. See more details
                # about lazy in the docstring of ConfigDict
                ConfigDict.lazy = False

            cfg = Config(
                cfg_dict,
                filename=filename,
                format_python_code=format_python_code)
            object.__setattr__(cfg, '_imported_names', imported_names)
            return cfg

    @staticmethod
    def _get_base_modules(nodes: list) -> list:
        """Get base module name from parsed code.

        Args:
            nodes (list): Parsed code of the config file.

        Returns:
            list: Name of base modules.
        """

        def _get_base_module_from_with(with_nodes: list) -> list:
            """Get base module name from if statement in python file.

            Args:
                with_nodes (list): List of if statement.

            Returns:
                list: Name of base modules.
            """
            base_modules = []
            for node in with_nodes:
                assert isinstance(node, ast.ImportFrom), (
                    'Illegal syntax in config file! Only '
                    '`from ... import ...` could be implemented` in '
                    'with read_base()`')
                assert node.module is not None, (
                    'Illegal syntax in config file! Syntax like '
                    '`from . import xxx` is not allowed in `with read_base()`')
                base_modules.append(node.level * '.' + node.module)
            return base_modules

        for idx, node in enumerate(nodes):
            if (isinstance(node, ast.Assign)
                    and isinstance(node.targets[0], ast.Name)
                    and node.targets[0].id == BASE_KEY):
                raise SyntaxError(
                    'The configuration file type in the inheritance chain '
                    'must match the current configuration file type, either '
                    '"lazy_import" or non-"lazy_import". You got this error '
                    f'since you use the syntax like `_base_ = "{node.targets[0].id}"` '  # noqa: E501
                    'in your config. You should use `with read_base(): ... to` '  # noqa: E501
                    'mark the inherited config file. See more information '# noqa: E501
                )

            if not isinstance(node, ast.With):
                continue

            expr = node.items[0].context_expr
            if (not isinstance(expr, ast.Call)
                    or not expr.func.id == 'read_base' or  # type: ignore
                    len(node.items) > 1):
                raise SyntaxError(
                    'Only `read_base` context manager can be used in the '
                    'config')
            for nested_idx, nested_node in enumerate(node.body):
                nodes.insert(idx + nested_idx + 1, nested_node)
            nodes.pop(idx)
            return _get_base_module_from_with(node.body)
        return []

    @staticmethod
    def _validate_py_syntax(filename: str):
        """Validate syntax of python config.

        Args:
            filename (str): Filename of python config file.
        """
        with open(filename, encoding='utf-8') as f:
            content = f.read()
        try:
            ast.parse(content)
        except SyntaxError as e:
            raise SyntaxError('There are syntax errors in config '
                              f'file {filename}: {e}')

    @staticmethod
    def _substitute_predefined_vars(filename: str, temp_config_name: str):
        """Substitute predefined variables in config with actual values.

        Sometimes we want some variables in the config to be related to the
        current path or file name, etc.

        Here is an example of a typical usage scenario. When training a model,
        we define a working directory in the config that save the models and
        logs. For different configs, we expect to define different working
        directories. A common way for users is to use the config file name
        directly as part of the working directory name, e.g. for the config
        ``config_setting1.py``, the working directory is
        ``. /work_dir/config_setting1``.

        This can be easily achieved using predefined variables, which can be
        written in the config `config_setting1.py` as follows

        .. code-block:: python

           work_dir = '. /work_dir/{{ fileBasenameNoExtension }}'


        Here `{{ fileBasenameNoExtension }}` indicates the file name of the
        config (without the extension), and when the config class reads the
        config file, it will automatically parse this double-bracketed string
        to the corresponding actual value.

        .. code-block:: python

           cfg = Config.fromfile('. /config_setting1.py')
           cfg.work_dir # ". /work_dir/config_setting1"


        For details, Please refer to docs/zh_cn/advanced_tutorials/config.md .

        Args:
            filename (str): Filename of config.
            temp_config_name (str): Temporary filename to save substituted
                config.
        """
        file_dirname = osp.dirname(filename)
        file_basename = osp.basename(filename)
        file_basename_no_extension = osp.splitext(file_basename)[0]
        file_extname = osp.splitext(filename)[1]
        support_templates = dict(
            fileDirname=file_dirname,
            fileBasename=file_basename,
            fileBasenameNoExtension=file_basename_no_extension,
            fileExtname=file_extname)
        with open(filename, encoding='utf-8') as f:
            config_file = f.read()
        for key, value in support_templates.items():
            regexp = r'\{\{\s*' + str(key) + r'\s*\}\}'
            value = value.replace('\\', '/')
            config_file = re.sub(regexp, value, config_file)
        with open(temp_config_name, 'w', encoding='utf-8') as tmp_config_file:
            tmp_config_file.write(config_file)

    @staticmethod
    def _substitute_env_variables(filename: str, temp_config_name: str):
        """Substitute environment variables in config with actual values.

        Sometimes, we want to change some items in the config with environment
        variables. For examples, we expect to change dataset root by setting
        ``DATASET_ROOT=/dataset/root/path`` in the command line. This can be
        easily achieved by writing lines in the config as follows

        .. code-block:: python

           data_root = '{{$DATASET_ROOT:/default/dataset}}/images'


        Here, ``{{$DATASET_ROOT:/default/dataset}}`` indicates using the
        environment variable ``DATASET_ROOT`` to replace the part between
        ``{{}}``. If the ``DATASET_ROOT`` is not set, the default value
        ``/default/dataset`` will be used.

        Environment variables not only can replace items in the string, they
        can also substitute other types of data in config. In this situation,
        we can write the config as below

        .. code-block:: python

           model = dict(
               bbox_head = dict(num_classes={{'$NUM_CLASSES:80'}}))


        For details, Please refer to docs/zh_cn/tutorials/config.md .

        Args:
            filename (str): Filename of config.
            temp_config_name (str): Temporary filename to save substituted
                config.
        """
        with open(filename, encoding='utf-8') as f:
            config_file = f.read()
        regexp = r'\{\{[\'\"]?\s*\$(\w+)\s*\:\s*(\S*?)\s*[\'\"]?\}\}'
        keys = re.findall(regexp, config_file)
        env_variables = dict()
        for var_name, value in keys:
            regexp = r'\{\{[\'\"]?\s*\$' + var_name + r'\s*\:\s*' \
                + value + r'\s*[\'\"]?\}\}'
            if var_name in os.environ:
                value = os.environ[var_name]
                env_variables[var_name] = value
            if not value:
                raise KeyError(f'`{var_name}` cannot be found in `os.environ`.'
                               f' Please set `{var_name}` in environment or '
                               'give a default value.')
            config_file = re.sub(regexp, value, config_file)

        with open(temp_config_name, 'w', encoding='utf-8') as tmp_config_file:
            tmp_config_file.write(config_file)
        return env_variables

    @staticmethod
    def _pre_substitute_base_vars(filename: str,
                                  temp_config_name: str) -> dict:
        """Preceding step for substituting variables in base config with actual
        value.

        Args:
            filename (str): Filename of config.
            temp_config_name (str): Temporary filename to save substituted
                config.

        Returns:
            dict: A dictionary contains variables in base config.
        """
        with open(filename, encoding='utf-8') as f:
            config_file = f.read()
        base_var_dict = {}
        regexp = r'\{\{\s*' + BASE_KEY + r'\.([\w\.]+)\s*\}\}'
        base_vars = set(re.findall(regexp, config_file))
        for base_var in base_vars:
            randstr = f'_{base_var}_{uuid.uuid4().hex.lower()[:6]}'
            base_var_dict[randstr] = base_var
            regexp = r'\{\{\s*' + BASE_KEY + r'\.' + base_var + r'\s*\}\}'
            config_file = re.sub(regexp, f'"{randstr}"', config_file)
        with open(temp_config_name, 'w', encoding='utf-8') as tmp_config_file:
            tmp_config_file.write(config_file)
        return base_var_dict

    @staticmethod
    def _substitute_base_vars(cfg: Any, base_var_dict: dict,
                              base_cfg: dict) -> Any:
        """Substitute base variables from strings to their actual values.

        Args:
            Any : Config dictionary.
            base_var_dict (dict): A dictionary contains variables in base
                config.
            base_cfg (dict): Base config dictionary.

        Returns:
            Any : A dictionary with origin base variables
                substituted with actual values.
        """
        cfg = copy.deepcopy(cfg)

        if isinstance(cfg, dict):
            for k, v in cfg.items():
                if isinstance(v, str) and v in base_var_dict:
                    new_v = base_cfg
                    for new_k in base_var_dict[v].split('.'):
                        new_v = new_v[new_k]
                    cfg[k] = new_v
                elif isinstance(v, (list, tuple, dict)):
                    cfg[k] = Config._substitute_base_vars(
                        v, base_var_dict, base_cfg)
        elif isinstance(cfg, tuple):
            cfg = tuple(
                Config._substitute_base_vars(c, base_var_dict, base_cfg)
                for c in cfg)
        elif isinstance(cfg, list):
            cfg = [
                Config._substitute_base_vars(c, base_var_dict, base_cfg)
                for c in cfg
            ]
        elif isinstance(cfg, str) and cfg in base_var_dict:
            new_v = base_cfg
            for new_k in base_var_dict[cfg].split('.'):
                new_v = new_v[new_k]
            cfg = new_v

        return cfg

    @staticmethod
    def _file2dict(
            filename: str,
            use_predefined_variables: bool = True,
            use_environment_variables: bool = True,
            lazy_import: Optional[bool] = None) -> Tuple[dict, str, dict]:
        """Transform file to variables dictionary.

        Args:
            filename (str): Name of config file.
            use_predefined_variables (bool, optional): Whether to use
                predefined variables. Defaults to True.
            use_environment_variables (bool, optional): Whether to use
                environment variables. Defaults to True.
            lazy_import (bool): Whether to load config in `lazy_import` mode.
                If it is `None`, it will be deduced by the content of the
                config file. Defaults to None.

        Returns:
            Tuple[dict, str]: Variables dictionary and text of Config.
        """
        if lazy_import is None and Config._is_lazy_import(filename):
            raise RuntimeError(
                'The configuration file type in the inheritance chain '
                'must match the current configuration file type, either '
                '"lazy_import" or non-"lazy_import". You got this error '
                'since you use the syntax like `with read_base(): ...` '
                f'or import non-builtin module in {filename}.'  # noqa: E501
            )

        filename = osp.abspath(osp.expanduser(filename))
        check_file_exist(filename)
        fileExtname = osp.splitext(filename)[1]
        if fileExtname not in ['.py', '.json', '.yaml', '.yml']:
            raise OSError('Only py/yml/yaml/json type are supported now!')
        try:
            with tempfile.TemporaryDirectory() as temp_config_dir:
                temp_config_file = tempfile.NamedTemporaryFile(
                    dir=temp_config_dir, suffix=fileExtname, delete=False)
                if platform.system() == 'Windows':
                    temp_config_file.close()

                # Substitute predefined variables
                if use_predefined_variables:
                    Config._substitute_predefined_vars(filename,
                                                       temp_config_file.name)
                else:
                    shutil.copyfile(filename, temp_config_file.name)
                # Substitute environment variables
                env_variables = dict()
                if use_environment_variables:
                    env_variables = Config._substitute_env_variables(
                        temp_config_file.name, temp_config_file.name)
                # Substitute base variables from placeholders to strings
                base_var_dict = Config._pre_substitute_base_vars(
                    temp_config_file.name, temp_config_file.name)

                # Handle base files
                base_cfg_dict = ConfigDict()
                cfg_text_list = list()
                for base_cfg_path in Config._get_base_files(
                        temp_config_file.name):
                    base_cfg_path, scope = Config._get_cfg_path(
                        base_cfg_path, filename)
                    _cfg_dict, _cfg_text, _env_variables = Config._file2dict(
                        filename=base_cfg_path,
                        use_predefined_variables=use_predefined_variables,
                        use_environment_variables=use_environment_variables,
                        lazy_import=lazy_import,
                    )
                    cfg_text_list.append(_cfg_text)
                    env_variables.update(_env_variables)
                    duplicate_keys = base_cfg_dict.keys() & _cfg_dict.keys()
                    if len(duplicate_keys) > 0:
                        raise KeyError(
                            'Duplicate key is not allowed among bases. '
                            f'Duplicate keys: {duplicate_keys}')

                    # _dict_to_config_dict will do the following things:
                    # 1. Recursively converts ``dict`` to :obj:`ConfigDict`.
                    # 2. Set `_scope_` for the outer dict variable for the base
                    # config.
                    # 3. Set `scope` attribute for each base variable.
                    # Different from `_scope_`, `scope` is not a key of base
                    # dict, `scope` attribute will be parsed to key `_scope_`
                    # by function `_parse_scope` only if the base variable is
                    # accessed by the current config.
                    _cfg_dict = Config._dict_to_config_dict(_cfg_dict, scope)
                    base_cfg_dict.update(_cfg_dict)

                if filename.endswith('.py'):
                    with open(temp_config_file.name, encoding='utf-8') as f:
                        parsed_codes = ast.parse(f.read())
                        parsed_codes = RemoveAssignFromAST(BASE_KEY).visit(
                            parsed_codes)
                    codeobj = compile(parsed_codes, filename, mode='exec')
                    # Support load global variable in nested function of the
                    # config.
                    global_locals_var = {BASE_KEY: base_cfg_dict}
                    ori_keys = set(global_locals_var.keys())
                    eval(codeobj, global_locals_var, global_locals_var)
                    cfg_dict = {
                        key: value
                        for key, value in global_locals_var.items()
                        if (key not in ori_keys and not key.startswith('__'))
                    }
                elif filename.endswith(('.yml', '.yaml', '.json')):
                    cfg = OmegaConf.load(temp_config_file.name)
                    cfg_dict = OmegaConf.to_container(cfg, resolve=True)
                # close temp file
                for key, value in list(cfg_dict.items()):
                    if isinstance(value,
                                  (types.FunctionType, types.ModuleType)):
                        cfg_dict.pop(key)
                temp_config_file.close()

                # If the current config accesses a base variable of base
                # configs, The ``scope`` attribute of corresponding variable
                # will be converted to the `_scope_`.
                Config._parse_scope(cfg_dict)
        except Exception as e:
            if osp.exists(temp_config_dir):
                shutil.rmtree(temp_config_dir)
            raise e

        # check deprecation information
        if DEPRECATION_KEY in cfg_dict:
            deprecation_info = cfg_dict.pop(DEPRECATION_KEY)
            warning_msg = f'The config file {filename} will be deprecated ' \
                'in the future.'
            if 'expected' in deprecation_info:
                warning_msg += f' Please use {deprecation_info["expected"]} ' \
                    'instead.'
            if 'reference' in deprecation_info:
                warning_msg += ' More information can be found at ' \
                    f'{deprecation_info["reference"]}'
            warnings.warn(warning_msg, DeprecationWarning)

        cfg_text = filename + '\n'
        with open(filename, encoding='utf-8') as f:
            # Setting encoding explicitly to resolve coding issue on windows
            cfg_text += f.read()

        # Substitute base variables from strings to their actual values
        cfg_dict = Config._substitute_base_vars(cfg_dict, base_var_dict,
                                                base_cfg_dict)
        cfg_dict.pop(BASE_KEY, None)

        cfg_dict = Config._merge_a_into_b(cfg_dict, base_cfg_dict)
        cfg_dict = {
            k: v
            for k, v in cfg_dict.items() if not k.startswith('__')
        }

        # merge cfg_text
        cfg_text_list.append(cfg_text)
        cfg_text = '\n'.join(cfg_text_list)

        return cfg_dict, cfg_text, env_variables

    @staticmethod
    def _parse_lazy_import(filename: str) -> Tuple[ConfigDict, set]:
        """Transform file to variables dictionary.

        Args:
            filename (str): Name of config file.

        Returns:
            Tuple[dict, dict]: ``cfg_dict`` and ``imported_names``.

              - cfg_dict (dict): Variables dictionary of parsed config.
              - imported_names (set): Used to mark the names of
                imported object.
        """
        # In lazy import mode, users can use the Python syntax `import` to
        # implement inheritance between configuration files, which is easier
        # for users to understand the hierarchical relationships between
        # different configuration files.

        # Besides, users can also using `import` syntax to import corresponding
        # module which will be filled in the `type` field. It means users
        # can directly navigate to the source of the module in the
        # configuration file by clicking the `type` field.

        # To avoid really importing the third party package like `torch`
        # during import `type` object, we use `_parse_lazy_import` to parse the
        # configuration file, which will not actually trigger the import
        # process, but simply parse the imported `type`s as LazyObject objects.

        # The overall pipeline of _parse_lazy_import is:
        # 1. Parse the base module from the config file.
        #                       ||
        #                       \/
        #       base_module = ['mmdet.configs.default_runtime']
        #                       ||
        #                       \/
        # 2. recursively parse the base module and gather imported objects to
        #    a dict.
        #                       ||
        #                       \/
        #       The base_dict will be:
        #       {
        #           'mmdet.configs.default_runtime': {...}
        #           'mmdet.configs.retinanet_r50_fpn_1x_coco': {...}
        #           ...
        #       }, each item in base_dict is a dict of `LazyObject`
        # 3. parse the current config file filling the imported variable
        #    with the base_dict.
        #
        # 4. During the parsing process, all imported variable will be
        #    recorded in the `imported_names` set. These variables can be
        #    accessed, but will not be dumped by default.

        with open(filename, encoding='utf-8') as f:
            global_dict = {'LazyObject': LazyObject, '__file__': filename}
            base_dict = {}

            parsed_codes = ast.parse(f.read())
            # get the names of base modules, and remove the
            # `with read_base():'` statement
            base_modules = Config._get_base_modules(parsed_codes.body)
            base_imported_names = set()
            for base_module in base_modules:
                # If base_module means a relative import, assuming the level is
                # 2, which means the module is imported like
                # "from ..a.b import c". we must ensure that c is an
                # object `defined` in module b, and module b should not be a
                # package including `__init__` file but a single python file.
                level = len(re.match(r'\.*', base_module).group())
                if level > 0:
                    # Relative import
                    base_dir = osp.dirname(filename)
                    module_path = osp.join(
                        base_dir, *(['..'] * (level - 1)),
                        f'{base_module[level:].replace(".", "/")}.py')
                else:
                    # Absolute import
                    module_list = base_module.split('.')
                    if len(module_list) == 1:
                        raise SyntaxError(
                            'The imported configuration file should not be '
                            f'an independent package {module_list[0]}. Here '
                            'is an example: '
                            '`with read_base(): from mmdet.configs.retinanet_r50_fpn_1x_coco import *`'  # noqa: E501
                        )
                    else:
                        package = module_list[0]
                        root_path = get_installed_path(package)
                        module_path = f'{osp.join(root_path, *module_list[1:])}.py'  # noqa: E501
                if not osp.isfile(module_path):
                    raise SyntaxError(
                        f'{module_path} not found! It means that incorrect '
                        'module is defined in '
                        f'`with read_base(): = from {base_module} import ...`, please '  # noqa: E501
                        'make sure the base config module is valid '
                        'and is consistent with the prior import '
                        'logic')
                _base_cfg_dict, _base_imported_names = Config._parse_lazy_import(  # noqa: E501
                    module_path)
                base_imported_names |= _base_imported_names
                # The base_dict will be:
                # {
                #     'mmdet.configs.default_runtime': {...}
                #     'mmdet.configs.retinanet_r50_fpn_1x_coco': {...}
                #     ...
                # }
                base_dict[base_module] = _base_cfg_dict

            # `base_dict` contains all the imported modules from `base_cfg`.
            # In order to collect the specific imported module from `base_cfg`
            # before parse the current file, we using AST Transform to
            # transverse the imported module from base_cfg and merge then into
            # the global dict. After the ast transformation, most of import
            # syntax will be removed (except for the builtin import) and
            # replaced with the `LazyObject`
            transform = ImportTransformer(
                global_dict=global_dict,
                base_dict=base_dict,
                filename=filename)
            modified_code = transform.visit(parsed_codes)
            modified_code, abs_imported = _gather_abs_import_lazyobj(
                modified_code, filename=filename)
            imported_names = transform.imported_obj | abs_imported
            imported_names |= base_imported_names
            modified_code = ast.fix_missing_locations(modified_code)
            exec(
                compile(modified_code, filename, mode='exec'), global_dict,
                global_dict)

            ret: dict = {}
            for key, value in global_dict.items():
                if key.startswith('__') or key in ['LazyObject']:
                    continue
                ret[key] = value
            # convert dict to ConfigDict
            cfg_dict = Config._dict_to_config_dict_lazy(ret)

            return cfg_dict, imported_names

    @staticmethod
    def _dict_to_config_dict_lazy(cfg: dict):
        """Recursively converts ``dict`` to :obj:`ConfigDict`. The only
        difference between ``_dict_to_config_dict_lazy`` and
        ``_dict_to_config_dict_lazy`` is that the former one does not consider
        the scope, and will not trigger the building of ``LazyObject``.

        Args:
            cfg (dict): Config dict.

        Returns:
            ConfigDict: Converted dict.
        """
        # Only the outer dict with key `type` should have the key `_scope_`.
        if isinstance(cfg, dict):
            cfg_dict = ConfigDict()
            for key, value in cfg.items():
                cfg_dict[key] = Config._dict_to_config_dict_lazy(value)
            return cfg_dict
        if isinstance(cfg, (tuple, list)):
            return type(cfg)(
                Config._dict_to_config_dict_lazy(_cfg) for _cfg in cfg)
        return cfg

    @staticmethod
    def _dict_to_config_dict(cfg: dict,
                             scope: Optional[str] = None,
                             has_scope=True):
        """Recursively converts ``dict`` to :obj:`ConfigDict`.

        Args:
            cfg (dict): Config dict.
            scope (str, optional): Scope of instance.
            has_scope (bool): Whether to add `_scope_` key to config dict.

        Returns:
            ConfigDict: Converted dict.
        """
        # Only the outer dict with key `type` should have the key `_scope_`.
        if isinstance(cfg, dict):
            if has_scope and 'type' in cfg:
                has_scope = False
                if scope is not None and cfg.get('_scope_', None) is None:
                    cfg._scope_ = scope  # type: ignore
            cfg = ConfigDict(cfg)
            dict.__setattr__(cfg, 'scope', scope)
            for key, value in cfg.items():
                cfg[key] = Config._dict_to_config_dict(
                    value, scope=scope, has_scope=has_scope)
        elif isinstance(cfg, tuple):
            cfg = tuple(
                Config._dict_to_config_dict(_cfg, scope, has_scope=has_scope)
                for _cfg in cfg)
        elif isinstance(cfg, list):
            cfg = [
                Config._dict_to_config_dict(_cfg, scope, has_scope=has_scope)
                for _cfg in cfg
            ]
        return cfg

    @staticmethod
    def _parse_scope(cfg: dict) -> None:
        """Adds ``_scope_`` to :obj:`ConfigDict` instance, which means a base
        variable.

        If the config dict already has the scope, scope will not be
        overwritten.

        Args:
            cfg (dict): Config needs to be parsed with scope.
        """
        if isinstance(cfg, ConfigDict):
            cfg._scope_ = cfg.scope
        elif isinstance(cfg, (tuple, list)):
            [Config._parse_scope(value) for value in cfg]
        else:
            return

    @staticmethod
    def _get_base_files(filename: str) -> list:
        """Get the base config file.

        Args:
            filename (str): The config file.

        Raises:
            TypeError: Name of config file.

        Returns:
            list: A list of base config.
        """
        file_format = osp.splitext(filename)[1]
        if file_format == '.py':
            Config._validate_py_syntax(filename)
            with open(filename, encoding='utf-8') as f:
                parsed_codes = ast.parse(f.read()).body

                def is_base_line(c):
                    return (isinstance(c, ast.Assign)
                            and isinstance(c.targets[0], ast.Name)
                            and c.targets[0].id == BASE_KEY)

                base_code = next((c for c in parsed_codes if is_base_line(c)),
                                 None)
                if base_code is not None:
                    base_code = ast.Expression(  # type: ignore
                        body=base_code.value)  # type: ignore
                    base_files = eval(compile(base_code, '',
                                              mode='eval'))  # type: ignore
                else:
                    base_files = []
        elif file_format in ('.yml', '.yaml', '.json'):
            cfg = OmegaConf.load(filename)
            cfg_dict = OmegaConf.to_container(cfg, resolve=True)
            base_files = cfg_dict.get(BASE_KEY, [])
        else:
            raise SyntaxError(
                'The config type should be py, json, yaml or '
                f'yml, but got {file_format}')
        base_files = base_files if isinstance(base_files,
                                              list) else [base_files]
        return base_files

    @staticmethod
    def _get_cfg_path(cfg_path: str,
                      filename: str) -> Tuple[str, Optional[str]]:
        """Get the config path from the current or external package.

        Args:
            cfg_path (str): Relative path of config.
            filename (str): The config file being parsed.

        Returns:
            Tuple[str, str or None]: Path and scope of config. If the config
            is not an external config, the scope will be `None`.
        """
        if '::' in cfg_path:
            # `cfg_path` startswith '::' means an external config path.
            # Get package name and relative config path.
            scope = cfg_path.partition('::')[0]
            package, cfg_path = _get_package_and_cfg_path(cfg_path)

            if not is_installed(package):
                raise ModuleNotFoundError(
                    f'{package} is not installed, please install {package} '
                    f'manually')

            # Get installed package path.
            package_path = get_installed_path(package)
            try:
                # Get config path from meta file.
                cfg_path = _get_external_cfg_path(package_path, cfg_path)
            except ValueError:
                # Since base config does not have a metafile, it should be
                # concatenated with package path and relative config path.
                cfg_path = _get_external_cfg_base_path(package_path, cfg_path)
            except FileNotFoundError as e:
                raise e
            return cfg_path, scope
        else:
            # Get local config path.
            cfg_dir = osp.dirname(filename)
            cfg_path = osp.join(cfg_dir, cfg_path)
            return cfg_path, None

    @staticmethod
    def _merge_a_into_b(a: dict,
                        b: dict,
                        allow_list_keys: bool = False) -> dict:
        """Merge dict ``a`` into dict ``b`` (non-inplace).

        Values in ``a`` will overwrite ``b``. ``b`` is copied first to avoid
        in-place modifications.

        Args:
            a (dict): The source dict to be merged into ``b``.
            b (dict): The origin dict to be fetch keys from ``a``.
            allow_list_keys (bool): If True, int string keys (e.g. '0', '1')
              are allowed in source ``a`` and will replace the element of the
              corresponding index in b if b is a list. Defaults to False.

        Returns:
            dict: The modified dict of ``b`` using ``a``.

        Examples:
            # Normally merge a into b.
            >>> Config._merge_a_into_b(
            ...     dict(obj=dict(a=2)), dict(obj=dict(a=1)))
            {'obj': {'a': 2}}

            # Delete b first and merge a into b.
            >>> Config._merge_a_into_b(
            ...     dict(obj=dict(_delete_=True, a=2)), dict(obj=dict(a=1)))
            {'obj': {'a': 2}}

            # b is a list
            >>> Config._merge_a_into_b(
            ...     {'0': dict(a=2)}, [dict(a=1), dict(b=2)], True)
            [{'a': 2}, {'b': 2}]
        """
        b = b.copy()
        for k, v in a.items():
            if allow_list_keys and k.isdigit() and isinstance(b, list):
                k = int(k)
                if len(b) <= k:
                    raise KeyError(f'Index {k} exceeds the length of list {b}')
                b[k] = Config._merge_a_into_b(v, b[k], allow_list_keys)
            elif isinstance(v, dict):
                if k in b and not v.pop(DELETE_KEY, False):
                    allowed_types: Union[Tuple, type] = (
                        dict, list) if allow_list_keys else dict
                    if not isinstance(b[k], allowed_types):
                        raise TypeError(
                            f'{k}={v} in child config cannot inherit from '
                            f'base because {k} is a dict in the child config '
                            f'but is of type {type(b[k])} in base config. '
                            f'You may set `{DELETE_KEY}=True` to ignore the '
                            f'base config.')
                    b[k] = Config._merge_a_into_b(v, b[k], allow_list_keys)
                else:
                    b[k] = ConfigDict(v)
            else:
                b[k] = v
        return b

    @property
    def filename(self) -> str:
        """Get file name of config."""
        return self._filename

    @property
    def text(self) -> str:
        """Get config text."""
        return self._text

    @property
    def env_variables(self) -> dict:
        """Get used environment variables."""
        return self._env_variables

    @property
    def pretty_text(self) -> str:
        """Get formatted python config text."""

        indent = 4

        def _indent(s_, num_spaces):
            s = s_.split('\n')
            if len(s) == 1:
                return s_
            first = s.pop(0)
            s = [(num_spaces * ' ') + line for line in s]
            s = '\n'.join(s)
            s = first + '\n' + s
            return s

        def _format_basic_types(k, v, use_mapping=False):
            if isinstance(v, str):
                v_str = repr(v)
            else:
                v_str = str(v)

            if use_mapping:
                k_str = f"'{k}'" if isinstance(k, str) else str(k)
                attr_str = f'{k_str}: {v_str}'
            else:
                attr_str = f'{str(k)}={v_str}'
            attr_str = _indent(attr_str, indent)

            return attr_str

        def _format_list_tuple(k, v, use_mapping=False):
            if isinstance(v, list):
                left = '['
                right = ']'
            else:
                left = '('
                right = ')'

            v_str = f'{left}\n'
            # check if all items in the list are dict
            for item in v:
                if isinstance(item, dict):
                    v_str += f'dict({_indent(_format_dict(item), indent)}),\n'
                elif isinstance(item, tuple):
                    v_str += f'{_indent(_format_list_tuple(None, item), indent)},\n'  # noqa: 501
                elif isinstance(item, list):
                    v_str += f'{_indent(_format_list_tuple(None, item), indent)},\n'  # noqa: 501
                elif isinstance(item, str):
                    v_str += f'{_indent(repr(item), indent)},\n'
                else:
                    v_str += str(item) + ',\n'
            if k is None:
                return _indent(v_str, indent) + right
            if use_mapping:
                k_str = f"'{k}'" if isinstance(k, str) else str(k)
                attr_str = f'{k_str}: {v_str}'
            else:
                attr_str = f'{str(k)}={v_str}'
            attr_str = _indent(attr_str, indent) + right
            return attr_str

        def _contain_invalid_identifier(dict_str):
            contain_invalid_identifier = False
            for key_name in dict_str:
                contain_invalid_identifier |= \
                    (not str(key_name).isidentifier())
            return contain_invalid_identifier

        def _format_dict(input_dict, outest_level=False):
            r = ''
            s = []

            use_mapping = _contain_invalid_identifier(input_dict)
            if use_mapping:
                r += '{'
            for idx, (k, v) in enumerate(
                    sorted(input_dict.items(), key=lambda x: str(x[0]))):
                is_last = idx >= len(input_dict) - 1
                end = '' if outest_level or is_last else ','
                if isinstance(v, dict):
                    v_str = '\n' + _format_dict(v)
                    if use_mapping:
                        k_str = f"'{k}'" if isinstance(k, str) else str(k)
                        attr_str = f'{k_str}: dict({v_str}'
                    else:
                        attr_str = f'{str(k)}=dict({v_str}'
                    attr_str = _indent(attr_str, indent) + ')' + end
                elif isinstance(v, (list, tuple)):
                    attr_str = _format_list_tuple(k, v, use_mapping) + end
                else:
                    attr_str = _format_basic_types(k, v, use_mapping) + end

                s.append(attr_str)
            r += '\n'.join(s)
            if use_mapping:
                r += '}'
            return r

        cfg_dict = self.to_dict()
        text = _format_dict(cfg_dict, outest_level=True)
        if self._format_python_code:
            # copied from setup.cfg
            yapf_style = dict(
                based_on_style='pep8',
                blank_line_before_nested_class_or_def=True,
                split_before_expression_after_opening_paren=True)
            try:
                from ...utils import digit_version
                if digit_version(yapf.__version__) >= digit_version('0.40.2'):
                    text, _ = FormatCode(text, style_config=yapf_style)
                else:
                    text, _ = FormatCode(
                        text, style_config=yapf_style, verify=True)
            except:  # noqa: E722
                raise SyntaxError('Failed to format the config file, please '
                                  f'check the syntax of: \n{text}')
        return text

    def __repr__(self):
        return f'Config (path: {self.filename}): {self._cfg_dict.__repr__()}'

    def __len__(self):
        return len(self._cfg_dict)

    def __getattr__(self, name: str) -> Any:
        return getattr(self._cfg_dict, name)

    def __getitem__(self, name):
        return self._cfg_dict.__getitem__(name)

    def __setattr__(self, name, value):
        if isinstance(value, dict):
            value = ConfigDict(value)
        self._cfg_dict.__setattr__(name, value)

    def __setitem__(self, name, value):
        if isinstance(value, dict):
            value = ConfigDict(value)
        self._cfg_dict.__setitem__(name, value)

    def __iter__(self):
        return iter(self._cfg_dict)

    def __getstate__(
            self
    ) -> Tuple[dict, Optional[str], Optional[str], dict, bool, set]:
        state = (self._cfg_dict, self._filename, self._text,
                 self._env_variables, self._format_python_code,
                 self._imported_names)
        return state

    def __deepcopy__(self, memo):
        cls = self.__class__
        other = cls.__new__(cls)
        memo[id(self)] = other

        for key, value in self.__dict__.items():
            super(Config, other).__setattr__(key, copy.deepcopy(value, memo))

        return other

    def __copy__(self):
        cls = self.__class__
        other = cls.__new__(cls)
        other.__dict__.update(self.__dict__)
        super(Config, other).__setattr__('_cfg_dict', self._cfg_dict.copy())

        return other

    copy = __copy__

    def __setstate__(self, state: Tuple[dict, Optional[str], Optional[str],
                                        dict, bool, set]):
        super().__setattr__('_cfg_dict', state[0])
        super().__setattr__('_filename', state[1])
        super().__setattr__('_text', state[2])
        super().__setattr__('_env_variables', state[3])
        super().__setattr__('_format_python_code', state[4])
        super().__setattr__('_imported_names', state[5])

    def dump(self, file: Optional[Union[str, Path]] = None):
        """Dump config to file or return config text.

        Args:
            file (str or Path, optional): If not specified, then the object
            is dumped to a str, otherwise to a file specified by the filename.
            Defaults to None.

        Returns:
            str or None: Config text.
        """
        file = str(file) if isinstance(file, Path) else file
        cfg_dict = self.to_dict()
        if file is None:
            if self.filename is None or self.filename.endswith('.py'):
                return self.pretty_text
            else:
                file_format = self.filename.split('.')[-1]
                return dump(cfg_dict, file_format=file_format)
        elif file.endswith('.py'):
            with open(file, 'w', encoding='utf-8') as f:
                f.write(self.pretty_text)
        else:
            file_format = file.split('.')[-1]
            return dump(cfg_dict, file=file, file_format=file_format)

    @staticmethod
    def _is_lazy_import(filename: str) -> bool:
        if not filename.endswith('.py'):
            return False
        with open(filename, encoding='utf-8') as f:
            codes_str = f.read()
            parsed_codes = ast.parse(codes_str)
        for node in ast.walk(parsed_codes):
            if (isinstance(node, ast.Assign)
                    and isinstance(node.targets[0], ast.Name)
                    and node.targets[0].id == BASE_KEY):
                return False

            if isinstance(node, ast.With):
                expr = node.items[0].context_expr
                if (not isinstance(expr, ast.Call)
                        or not expr.func.id == 'read_base'):  # type: ignore
                    raise SyntaxError(
                        'Only `read_base` context manager can be used in the '
                        'config')
                return True
            if isinstance(node, ast.ImportFrom):
                # relative import -> lazy_import
                if node.level != 0:
                    return True
                # Skip checking when using `mmengine.config` in cfg file
                if (node.module == 'mmengine' and len(node.names) == 1
                        and node.names[0].name == 'Config'):
                    continue
                if not isinstance(node.module, str):
                    continue
                # non-builtin module -> lazy_import
                if not _is_builtin_module(node.module):
                    return True
            if isinstance(node, ast.Import):
                for alias_node in node.names:
                    if not _is_builtin_module(alias_node.name):
                        return True
        return False

    def _to_lazy_dict(self, keep_imported: bool = False) -> dict:
        """Convert config object to dictionary with lazy object, and filter the
        imported object."""
        res = self._cfg_dict._to_lazy_dict()
        if hasattr(self, '_imported_names') and not keep_imported:
            res = {
                key: value
                for key, value in res.items()
                if key not in self._imported_names
            }
        return res

    def to_dict(self, keep_imported: bool = False):
        """Convert all data in the config to a builtin ``dict``.

        Args:
            keep_imported (bool): Whether to keep the imported field.
                Defaults to False

        If you import third-party objects in the config file, all imported
        objects will be converted to a string like ``torch.optim.SGD``
        """
        cfg_dict = self._cfg_dict.to_dict()
        if hasattr(self, '_imported_names') and not keep_imported:
            cfg_dict = {
                key: value
                for key, value in cfg_dict.items()
                if key not in self._imported_names
            }
        return cfg_dict