public static function getGroupAndItemLabelsFromSerial($serial) {
        $sels = unserialize($serial);
        if (empty($sels['comboSetId']) || empty($sels['comboSetItems'])) {
            return null;
        }

        $grouplabelmap = [];
        $itemlabelmap = [];
        foreach ($sels['comboSetItems'] as $giserial => $gitem) {
            $gisels = unserialize($giserial);
            $group = ComboGroup::getComboGroupById($gisels['groupId']);
            $item = GroupItem::getGroupItemById($gisels['itemId']);
            $grouplabelmap[$group->getId()] = $group->getLabel();
            $itemlabelmap[$item->getId()] = $item->getItemLabel();
        }

        return [
            'grouplabelmap' => $grouplabelmap,
            'itemlabelmap' => $itemlabelmap,
        ];
    }