public function updateGuestQuantityAsyncWithHttpInfo($checkout_session_id, $x_ebay_c_marketplace_id, $update_quantity = null)
    {
        $returnType = '\TNT\Ebay\Buy\Order\V2\Model\GuestCheckoutSessionResponseV2';
        $request = $this->updateGuestQuantityRequest($checkout_session_id, $x_ebay_c_marketplace_id, $update_quantity);