public static function addDataGroupItemDownloadBtns($html, $umhs, $cart_row, $i) {
        if (!defined('WCEX_DLSELLER')) {
            return $html;
        }

        $sels = unserialize($cart_row['cart_serial']);
        // combo-set ID not set, continue
        if (empty($sels['comboSetId'])) {
            return $html;
        }
        // combo-set group items not set, continue
        if (!isset($sels['comboSetItems'])) {
            return $html;
        }

        $subhtml = '';
        $ordercart = wcexics_api_get_combo_set_ordercartdata($umhs['ID']);
        foreach ($ordercart as $cscart) {
            $division = dlseller_get_division($cscart['post_id']);
            if ($division !== 'data') {
                continue;
            }
            if ((int)$cscart['combo_set_cart_id'] === (int)$cart_row['cart_id']) {
                $subhtml .= '<tr>';
                $subhtml .= '<th>';
                $subhtml .= $cscart['sku_code'] . ' - ' . $cscart['sku_name'];
                $subhtml .= '</th>';
                $subhtml .= '<td>';
                $fd = new FileDownloads();
                add_filter('dlseller_filter_download_para', [$fd, 'filterGroupItemDownloadUrlParams'], 10, 2);
                $subhtml .= dlseller_filter_history_item_name('', $umhs, $cscart, $i);
                remove_filter('dlseller_filter_download_para', [$fd, 'filterGroupItemDownloadUrlParams'], 10);
                $subhtml .= '</td>';
                $subhtml .= '</tr>';
            }
        }

        if (!empty($subhtml)) {
            $subhtml = '<div class="avc-v3 mt-2rem wcexics gi-dl"><table>' . $subhtml . '</table></div>';
        }

        return $html . $subhtml;
    }