docs: def on_packet_received(self, pkt):
          """DEV: entry point. Will be called by sniff() for each
          received packet (that passes the filters).
          """
          if not pkt:
              return
          if self.store:
              self.lst.append(pkt)
          if self.prn:
              result = self.prn(pkt)
              if result is not None:
                  print(result)