Connect to redis and cache the new connection

def connect(self, **settings):
        """
        Connect to redis and cache the new connection
        """
        # compute a unique key for this settings, for caching. Work on the whole
        # dict without directly using known keys to allow the use of unix socket
        # connection or any other (future ?) way to connect to redis
        if not settings:
            settings = self.connection_settings
        connection_key = ':'.join([str(settings[k]) for k in sorted(settings)])
        if connection_key not in self._connections:
            self._connections[connection_key] = redis.StrictRedis(
                                            decode_responses=True, **settings)
        return self._connections[connection_key]