public function sharedMaxAge($seconds = null)
    {
        deprecationWarning(
            'Response::sharedMaxAge() is deprecated. ' .
            'Use withSharedMaxAge() instead.'
        );
        if ($seconds !== null) {
            $this->_cacheDirectives['s-maxage'] = $seconds;
            $this->_setCacheControl();
        }
        if (isset($this->_cacheDirectives['s-maxage'])) {
            return $this->_cacheDirectives['s-maxage'];
        }

        return null;
    }