public function getAclUrl(bool $refresh = false): string {
        if ($refresh || $this->aclUrl === null) {
            $request  = new Request('HEAD', $this->fedora->sanitizeUri($this->uri));
            $response = $this->fedora->sendRequest($request);
            $this->extractAcl($response);

            // Fedora 4.7.5 doesn't provide ACL link header for binary resources
            // if the ACL id directly attached to the resource (sic!).
            // As a fallback we can try to extract it from the metadata (which
            // is done automatically in the setMetadata() method being called
            // by the getMetadata(true) method).
            if ($this->aclUrl == '') {
                $this->getMetadata(true);
            }
        }
        return $this->aclUrl;
    }