public function getResponse(Checkout $checkout)
 {
     if (!$checkout->getEmail() && $this->options->getEmail()) {
         $checkout->setEmail($this->options->getEmail());
     }
     if (!$checkout->getExtraAmount() && $this->options->getExtraAmount()) {
         $checkout->setExtraAmount($this->options->getExtraAmount());
     }
     if (!$checkout->getMaxAge() && $this->options->getMaxAge()) {
         $checkout->setMaxAge($this->options->getMaxAge());
     }
     if (!$checkout->getMaxUses() && $this->options->getMaxUses()) {
         $checkout->setMaxUses($this->options->getMaxUses());
     }
     if (!$checkout->getNotificationURL() && $this->options->getNotificationURL()) {
         $checkout->setNotificationURL($this->options->getNotificationURL());
     }
     if (!$checkout->getRedirectURL() && $this->options->getRedirectURL()) {
         $checkout->setRedirectURL($this->options->getRedirectURL());
     }
     $code = $this->send($checkout);
     return $this->options->getPaymentUrl($code);
 }