code: def _redis_connect(cls, settings):
          
          if 'tornadoredis' not in globals():
              import tornadoredis
          kwargs = {'host': settings.get('host', cls.REDIS_HOST),
                    'port': settings.get('port', cls.REDIS_PORT),
                    'selected_db': settings.get('db', cls.REDIS_DB)}
          LOGGER.info('Connecting to %(host)s:%(port)s DB %(selected_db)s',
                      kwargs)
          cls._redis_client = tornadoredis.Client(**kwargs)
          cls._redis_client.connect()
docs: Connect to redis and assign the client to the RedisSession class
          so that it is globally available in this process.
  
          :param dict settings: The redis session configuration