docs: def latency(self):
          """ Checks the connection latency. """
          with self.lock:
              self.send('PING %s' % self.server)
              ctime = self._m_time.time()
  
              msg = self._recv(expected_replies=('PONG',))
              if msg[0] == 'PONG':
                  latency = self._m_time.time() - ctime
                  return latency