public function objectUrl($object, $defaultIfNotFound = null)
    {
        try {
            $ret = $this->provider->url($object);
        } catch (UnsupportedException $e) {
            if (null === $defaultIfNotFound) {
                throw $e;
            } else {
                if (true === $defaultIfNotFound) {
                    $ret = (string)$object;
                } else {
                    $ret = $defaultIfNotFound;
                }
            }
        }
        return $ret;
    }