Take already unpacked header and binary payload of received request reply and creates message instance
        :param header: a namedtuple header object providing header information
        :param payload: payload (BytesIO instance) of message

def unpack_reply(cls, header, payload):
        """Take already unpacked header and binary payload of received request reply and creates message instance
        :param header: a namedtuple header object providing header information
        :param payload: payload (BytesIO instance) of message
        """
        reply = cls(
            header.session_id, header.packet_count,
            segments=tuple(ReplySegment.unpack_from(payload, expected_segments=header.num_segments)),
            header=header
        )
        trace(reply)
        return reply