code: def validate_packet(packet):
      
      if not isinstance(packet, bytes):
          raise UnpackException('invalid packet')
  
      packet_length = len(packet)
  
      if packet_length < 8 or packet_length > 2**16:
          raise UnpackException('invalid packet')
  
      if packet_length != int.from_bytes(packet[2:4], byteorder='big'):
          raise UnpackException('invalid packet')
  
      version = packet[0]
      if version == 0 or version >= 128:
          raise UnpackException('invalid packet')
docs: Check if packet is valid OF packet.
  
      Raises:
          UnpackException: If the packet is invalid.