public function listPagePrivileges(PageOrder $pageOrder = null)
    {
        $this->initialize();
        if ($this->hasRootPrivileges() || $this->hasSitePrivileges()) {
            return array();
        }
        $returnArray = array();

        foreach ($this->pagePrivilege as $key => $val) {
            if ($pageOrder instanceof PageOrder) {
                $returnArray[] = $pageOrder->getPage($key);
            } else {
                $returnArray[] = $key;
            }
        }
        return $returnArray;
    }