If ``cls.key`` is not :obj:`None` and that is in config returns config with that argument.

        :param full_config:
        :return:

def validate(cls, full_config: typing.Dict[str, typing.Any]) -> typing.Dict[str, typing.Any]:
        """
        If ``cls.key`` is not :obj:`None` and that is in config returns config with that argument.

        :param full_config:
        :return:
        """
        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}