public static function addSettingsPage() {
        if (!current_user_can('manage_options')) {
            wp_die(__('You do not have sufficient permissions to access this page.'));
        }

        if (isset($_POST['wcexics_update_options']) && (int)wp_unslash(sanitize_text_field($_POST['wcexics_update_options'])) === 1) {
            $opts = self::getOptions();
            if (isset($_POST[self::ENABLE_ITEMCSV_OPT])) {
                $optv = trim(wp_unslash(sanitize_text_field($_POST[self::ENABLE_ITEMCSV_OPT])));
                if ($optv === 'yes' || $optv === 'no') {
                    $opts[self::ENABLE_ITEMCSV_OPT] = $optv;
                }
            }

            update_option(self::OPTION_KEY, $opts);
        }

        ?>
        <div class="wrap">
            <h1><?php esc_html_e('WCEX Item Combo-Set', 'wcexics'); ?></h1>
            <form method="post" action="">
                <?php settings_fields(self::OPTION_KEY); ?>
                <table class="form-table" role="presentation">
                    <?php self::enableItemCSVSection(); ?>
                </table>
                <input type="hidden" name="wcexics_update_options" value="1" />
                <?php submit_button(); ?>
            </form>
        </div>
        <?php
    }