code: def alertingNetToMs(Facility_presence=0, ProgressIndicator_presence=0,
                      UserUser_presence=0):
      
      a = TpPd(pd=0x3)
      b = MessageType(mesType=0x1)  # 00000001
      packet = a / b
      if Facility_presence is 1:
          c = FacilityHdr(ieiF=0x1C)
          packet = packet / c
      if ProgressIndicator_presence is 1:
          d = ProgressIndicatorHdr(ieiPI=0x1E)
          packet = packet / d
      if UserUser_presence is 1:
          e = UserUserHdr(ieiUU=0x7E)
          packet = packet / e
      return packet
docs: ALERTING Section 9.3.1.1