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

        $csgt = Schema::getComboSetGroupsTable();
        $group = $wpdb->get_row(
            $wpdb->prepare("SELECT * FROM {$csgt} cg WHERE cg.ID = %d", $id),
            ARRAY_A
        );

        if (empty($group)) {
            return null;
        }

        $items = GroupItem::getAllGroupItemsByComboGroupId($id);
        if (empty($items)) {
            $items = [];
        }

        return new ComboGroupType(
            $group['ID'],
            $group['combo_set_id'],
            $group['group_label'],
            (bool)(int)$group['optional'],
            (bool)(int)$group['allow_multiple_selections'],
            $group['position'],
            $items,
            $group['created_at'],
            $group['updated_at']
        );
    }