class_docstr: A dictionary that lazily load its values when they are requested.
class_docstr_tok: ["A","dictionary","that","lazily","load","its","values","when","they","are","requested","."]
code: def __getitem__(self, key):
      if key not in self._mapping:
          raise KeyError(key)
      value = self._mapping[key]
      module_name = model_type_to_module_name(key)
      if module_name not in self._modules:
          self._modules[module_name] = importlib.import_module(
              f".{module_name}", "fastNLP.transformers.torch.models"
          )
      return getattr(self._modules[module_name], value)
  
imports: import importlib
  import re
  from collections import OrderedDict
  from typing import List, Union
  from fastNLP.transformers.torch.configuration_utils import PretrainedConfig
  from fastNLP.transformers.torch.file_utils import CONFIG_NAME
  from fastNLP.core.log import logger
label_desc: Use image node_id 2 for calling the _LazyConfigMapping obj's underlying member method code with example usage: obj.__getitem__(key) and returns: getattr