Gets a single packet by its identifying key (gentime, seqNum).

        :param ~datetime.datetime generation_time: When the packet was generated (packet time)
        :param int sequence_number: Sequence number of the packet
        :rtype: .Packet

def get_packet(self, generation_time, sequence_number):
        """
        Gets a single packet by its identifying key (gentime, seqNum).

        :param ~datetime.datetime generation_time: When the packet was generated (packet time)
        :param int sequence_number: Sequence number of the packet
        :rtype: .Packet
        """
        url = '/archive/{}/packets/{}/{}'.format(
            self._instance, to_isostring(generation_time), sequence_number)
        response = self._client.get_proto(url)
        message = yamcs_pb2.TmPacketData()
        message.ParseFromString(response.content)
        return Packet(message)