public function setSiteTarget(CNabuSiteTarget $nb_site_target = null, $field = NABU_SITE_TARGET_FIELD_ID)
    {
        $this->nb_site_target = $nb_site_target;
        if ($this instanceof CNabuDataObject) {
            if ($nb_site_target instanceof CNabuSiteTarget) {
                $this->transferValue($nb_site_target, NABU_SITE_TARGET_FIELD_ID, $field);
            } else {
                $this->setValue($field, null);
            }
        }

        return $this;
    }