public function setSiteMap(CNabuSiteMap $nb_site_map, $field = NABU_SITE_MAP_FIELD_ID)
    {
        $this->nb_site_map = $nb_site_map;
        if ($this instanceof CNabuDataObject) {
            $this->transferValue($nb_site_map, NABU_SITE_MAP_FIELD_ID, $field);
        }

        return $this;
    }