src/transformers/models/auto/auto_factory.py/_LazyAutoMapping/__getitem__
class _LazyAutoMapping:    def __getitem__(self, key):
        model_type = self._reverse_config_mapping[key.__name__]
        if model_type not in self._model_mapping:
            raise KeyError(key)
        model_name = self._model_mapping[model_type]
        return self._load_attr_from_module(model_type, model_name)