public function get_ancestors() {
        global $DB;
        $ancestors = array();
        $ancestorsids = explode('/', trim($this->get('path'), '/'));
        // Drop the root item from the array /0/.
        array_shift($ancestorsids);
        if (!empty($ancestorsids)) {
            list($insql, $params) = $DB->get_in_or_equal($ancestorsids, SQL_PARAMS_NAMED);
            $ancestors = self::get_records_select("id $insql", $params);
        }
        return $ancestors;
    }