code: def connect(self):
          
          LOGGER.debug('Creating a%s connection to %s:%s (db %s)',
                       ' cluster node'
                       if self._clustering else '', self._hosts[0]['host'],
                       self._hosts[0]['port'], self._hosts[0].get(
                           'db', DEFAULT_DB))
          self._connect_future = concurrent.Future()
          conn = _Connection(
              self._hosts[0]['host'],
              self._hosts[0]['port'],
              self._hosts[0].get('db', DEFAULT_DB),
              self._read,
              self._on_closed,
              self.io_loop,
              cluster_node=self._clustering)
          self.io_loop.add_future(conn.connect(), self._on_connected)
          return self._connect_future
docs: Connect to the Redis server or Cluster.
  
          :rtype: tornado.concurrent.Future