public static function getAllGroupItemsByComboGroupId($id) {
        global $wpdb;

        $csgit = Schema::getComboSetGroupItemsTable();
        $itemids = $wpdb->get_results(
            $wpdb->prepare("SELECT ID FROM {$csgit} WHERE group_id = %d ORDER BY position ASC", $id),
            ARRAY_A
        );

        if ($itemids === null) {
            return Master::getErrorStore()->getErrorResponse(ErrorStore::INTERNAL_SERVER_ERROR);
        }

        $items = [];
        foreach ($itemids as $itemid) {
            $item = self::getGroupItemById($itemid['ID']);
            if (!empty($item)) {
                $items[] = $item;
            }
        }

        return $items;
    }