public function copyAssetFiles(&$replacementList){
        $object = $this->object;
        $portableAssetsToExport = [];
        $service = new PortableElementService();
        $service->setServiceLocator(ServiceManager::getServiceManager());
        $files = $object->getModel()->getValidator()->getAssets($object, 'runtime');
        $baseUrl = $this->qtiItemExporter->buildBasePath() . DIRECTORY_SEPARATOR . $object->getTypeIdentifier();
        foreach ($files as $url) {
            // Skip shared libraries into portable element
            if (strpos($url, './') !== 0) {
                \common_Logger::i('Shared libraries skipped : ' . $url);
                $portableAssetsToExport[$url] = $url;
                continue;
            }
            $stream = $service->getFileStream($object, $url);
            $replacement = $this->qtiItemExporter->copyAssetFile($stream, $baseUrl, $url, $replacementList);
            $portableAssetToExport = preg_replace('/^(.\/)(.*)/', $object->getTypeIdentifier() . "/$2", $replacement);
            $portableAssetsToExport[$url] = $portableAssetToExport;
            \common_Logger::i('File copied: "' . $url . '" for portable element ' . $object->getTypeIdentifier());
        }
        return $this->portableAssetsToExport = $portableAssetsToExport;
    }