public function expires($time = null)
    {
        deprecationWarning(
            'Response::expires() is deprecated. ' .
            'Use withExpires() instead.'
        );

        if ($time !== null) {
            $date = $this->_getUTCDate($time);
            $this->_setHeader('Expires', $date->format('D, j M Y H:i:s') . ' GMT');
        }

        if ($this->hasHeader('Expires')) {
            return $this->getHeaderLine('Expires');
        }

        return null;
    }