<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _is_json_serialized_jws(self, json_jws):
 """ Check if we've got a JSON serialized signed JWT. :param json_jws: The message :return: True/False """

        json_ser_keys = {"payload", "signatures"}
        flattened_json_ser_keys = {"payload", "signature"}
        if not json_ser_keys.issubset(
                json_jws.keys()) and not flattened_json_ser_keys.issubset(
                json_jws.keys()):
            return False
        return True