public function setRedis(?RedisClient $redis = null)
    {
        if (! $redis) {
            $server = Arr::get($this->config, 'server', []);
            $options = Arr::get($this->config, 'options', []);

            // forbid setting prefix from options
            if (Arr::has($options, 'prefix')) {
                $options = Arr::except($options, 'prefix');
            }

            $redis = new RedisClient($server, $options);
        }

        $this->redis = $redis;
    }