public function getChildBookmarksCount($parent)
    {

        $strURI = Product::$baseProductUri . '/pdf/' . $this->getFileName() . '/bookmarks/' . $parent . '/bookmarks';
        $signedURI = Utils::sign($strURI);
        $responseStream = Utils::processCommand($signedURI, 'GET', '', '');
        $json = json_decode($responseStream);
        return count($json->Bookmarks->List);
    }