code: def validate(cls, full_config: typing.Dict[str, typing.Any]) -> typing.Dict[str, typing.Any]:
          
          if cls.key is not None:
              if cls.key in full_config:
                  return {cls.key: full_config[cls.key]}
              elif cls.required:
                  return {cls.key: cls.default}
docs: If ``cls.key`` is not :obj:`None` and that is in config returns config with that argument.
  
          :param full_config:
          :return: