public function vary($cacheVariances = null)
    {
        deprecationWarning(
            'Response::vary() is deprecated. ' .
            'Use withVary() instead.'
        );

        if ($cacheVariances !== null) {
            $cacheVariances = (array)$cacheVariances;
            $this->_setHeader('Vary', implode(', ', $cacheVariances));
        }

        if ($this->hasHeader('Vary')) {
            return explode(', ', $this->getHeaderLine('Vary'));
        }

        return null;
    }