private function getSparqlTriples(Resource $metadata): string {
        $uri = $this->fedora->sanitizeUri($this->uri);
        $res = $metadata->copy(self::$skipProp, self::$skipPropRegExp, $uri);

        // make sure the ACL property is in current transaction
        $aclProp = $res->getResource(WebAcl::ACL_LINK_PROP);
        if ($aclProp) {
            $res->deleteResource(WebAcl::ACL_LINK_PROP);
            if ($aclProp->getUri() !== 'http://fedora.info/definitions/v4/repository#inaccessibleResource') {
                $res->addResource(WebAcl::ACL_LINK_PROP, $this->fedora->sanitizeUri($aclProp->getUri()));
            }
        }

        $rdf = $res->getGraph()->serialise('ntriples');
        return $rdf;
    }