static public function getPropertyStorageMap($triples)
    {
        $referencer = ServiceManager::getServiceManager()->get(FileReferenceSerializer::SERVICE_ID);
        $map = [];
        foreach ($triples as $triple) {
            if (self::isFileReference($triple)) {
                $source = $referencer->unserialize($triple->object);
                $map[$triple->predicate] = $source->getFileSystemId();
            }
        }
        return $map;
    }