docs: def send_packet(self):
          """Write next packet in send queue."""
          waiter, packet = self.client.waiters.popleft()
          self.logger.debug('sending packet: %s', binascii.hexlify(packet))
          self.client.active_transaction = waiter
          self.client.in_transaction = True
          self.client.active_packet = packet
          self.reset_cmd_timeout()
          self.transport.write(packet)