/**
  * {@inheritDoc}
  */
 public function savePaymentInformation($cartId, $email, \Magento\Quote\Api\Data\PaymentInterface $paymentMethod, \Magento\Quote\Api\Data\AddressInterface $billingAddress)
 {
     $billingAddress->setEmail($email);
     $this->billingAddressManagement->assign($cartId, $billingAddress);
     $this->paymentMethodManagement->set($cartId, $paymentMethod);
     return true;
 }
 /**
  * {@inheritDoc}
  */
 public function savePaymentInformation($cartId, $email, \Magento\Quote\Api\Data\PaymentInterface $paymentMethod, \Magento\Quote\Api\Data\AddressInterface $billingAddress = null)
 {
     if ($billingAddress) {
         $billingAddress->setEmail($email);
         $this->billingAddressManagement->assign($cartId, $billingAddress);
     } else {
         $quoteIdMask = $this->quoteIdMaskFactory->create()->load($cartId, 'masked_id');
         $this->cartRepository->getActive($quoteIdMask->getQuoteId())->getBillingAddress()->setEmail($email);
     }
     $this->paymentMethodManagement->set($cartId, $paymentMethod);
     return true;
 }