public function onComplete(CompleteEvent $event)
    {
        $request = $event->getRequest();
        $response = $event->getResponse();

        // Cache the response if it can be cached and isn't already
        if ($request->getConfig()->get('cache_lookup') === 'MISS'
            && call_user_func($this->canCache, $request)
            && Utils::canCacheResponse($response)
        ) {
            // Store the date when the response was cached
            $response->setHeader('X-Guzzle-Cache-Date', gmdate('D, d M Y H:i:s T', time()));
            $this->storage->cache($request, $response);
        }

        $this->addResponseHeaders($request, $response);
    }