<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_tp(pkt):
 """Returns true if pkt is using SOMEIP-TP, else returns false."""


        tp = [SOMEIP.TYPE_TP_REQUEST, SOMEIP.TYPE_TP_REQUEST_NO_RET,
              SOMEIP.TYPE_TP_NOTIFICATION, SOMEIP.TYPE_TP_RESPONSE,
              SOMEIP.TYPE_TP_ERROR]
        if isinstance(pkt, Packet):
            return pkt.msg_type in tp
        else:
            return pkt[15] in tp