code: def _valid_packet(raw_packet):
          
          if raw_packet[0:1] != b'\xcc':
              return False
          if len(raw_packet) != 19:
              return False
          checksum = 0
          for i in range(1, 17):
              checksum += raw_packet[i]
          if checksum != raw_packet[18]:
              return False
          return True
docs: Validate incoming packet.