public function getSiteMap($nb_site_map, $cascade = false)
    {
        $retval = null;

        $nb_site_map_id = nb_getMixedValue($nb_site_map, 'nb_site_map_id');
        if (is_numeric($nb_site_map_id) || nb_isValidGUID($nb_site_map_id)) {
            $retval = $this->nb_site_map_tree->getItem($nb_site_map_id);
        }

        return $retval;
    }