protected function getAssets(\core_kernel_classes_Resource $item, $lang)
    {
        $qtiItem = Service::singleton()->getDataItemByRdfItem($item, $lang);
        if (is_null($qtiItem)) {
            return [];
        }
        $assetParser = new AssetParser($qtiItem, $this->getStorageDirectory($item, $lang));
        $assetParser->setGetSharedLibraries(false);
        $returnValue = array();
        foreach ($assetParser->extract() as $type => $assets) {
            foreach ($assets as $assetUrl) {
                foreach (self::$BLACKLIST as $blacklist) {
                    if (preg_match($blacklist, $assetUrl) === 1) {
                        continue(2);
                    }
                }
                $returnValue[] = $assetUrl;
            }
        }
        return $returnValue;
    }