public function setLastModified(Request $request, \DateTime $lastModified)
    {
        $this->cache->save($this->getCacheKeyRequest(sha1($request->getUri()), 'lastmodified'), $lastModified->format('r'));

        foreach ($this->itemIds as $itemId => $bool) {
            $key                             = $this->getCacheKeyItem($itemId, 'uri');
            $urisForItem                     = Option::fromValue($this->cache->fetch($key), false)->getOrElse(array());
            $urisForItem[$request->getUri()] = $bool;
            $this->cache->save($key, $urisForItem);
            Option::fromValue($this->logger)->map(function (LoggerInterface $logger) use ($request, $itemId) {
                $logger->debug(sprintf('[ContentfulBundle:RequestLastModifiedCache] "%s" is used on "%s".', $itemId, $request->getUri()));
            });
        }
    }