def publish_message(self, message, expire=None):
        """
        Publish a ``message`` on the subscribed channel on the Redis datastore.
        ``expire`` sets the time in seconds, on how long the message shall additionally of being
        published, also be persisted in the Redis datastore. If unset, it defaults to the
        configuration settings ``WS4REDIS_EXPIRE``.
        """
        if expire is None:
            expire = self._expire
        if not isinstance(message, RedisMessage):
            raise ValueError('message object is not of type RedisMessage')
        for channel in self._publishers:
            self._connection.publish(channel, message)
            if expire > 0:
                self._connection.setex(channel, expire, message)

        Publish a ``message`` on the subscribed channel on the Redis datastore.
        ``expire`` sets the time in seconds, on how long the message shall additionally of being
        published, also be persisted in the Redis datastore. If unset, it defaults to the
        configuration settings ``WS4REDIS_EXPIRE``.
        
ws4redis/redis_store.py