code: def address_family(self):
          
          if len(self.raw) >= 20:
              v = i(self.raw[0]) >> 4
              if v == 4:
                  return socket.AF_INET
              if v == 6:
                  return socket.AF_INET6
docs: The packet address family:
              - socket.AF_INET, if IPv4
              - socket.AF_INET6, if IPv6
              - None, otherwise.