docs: def guess_payload_class(self, payload):
          """
          Handles NTPv4 extensions and MAC part (when authentication is used.)
          """
          plen = len(payload)
  
          if plen > _NTP_AUTH_MD5_TAIL_SIZE:
              return NTPExtensions
          elif plen == _NTP_AUTH_MD5_TAIL_SIZE:
              return NTPAuthenticator
  
          return Packet.guess_payload_class(self, payload)