public function markingClasses() {
        $classes='';
        if(!$this->isExpanded()) {
            $classes .= " unexpanded jstree-closed";
        }
        if($this->isTreeOpened()) {
            if($this->numChildren() > 0) $classes .= " jstree-open";
        } else {
            $classes .= " closed";
        }
        return $classes;
    }