docs: def maybeReceiveAck(self, ackPacket):
          """
          Receive an L{ack} or L{synAck} input from the given packet.
          """
          ackPredicate = self.ackPredicate
          self.ackPredicate = lambda packet: False
          if ackPacket.syn:
              # New SYN packets are always news.
              self.synAck()
              return
          if ackPredicate(ackPacket):
              self.ack()