docs: def mustRetransmit(self):
          """
          Check to see if this packet must be retransmitted until it was
          received.
  
          Packets which contain a connection-state changing flag (SYN or FIN) or
          a non-zero amount of data can be retransmitted.
          """
          if self.syn or self.fin or self.dlen:
              return True
          return False