code: @Nullable
      public PaymentIntent confirmPaymentIntentSynchronous(
              @NonNull PaymentIntentParams paymentIntentParams,
              @NonNull String publishableKey) throws AuthenticationException,
              InvalidRequestException,
              APIConnectionException,
              APIException {
          return mApiHandler.confirmPaymentIntent(
                  paymentIntentParams,
                  publishableKey,
                  mStripeAccount
          );
      }
docs: Blocking method to confirm a {@link PaymentIntent} object.
  Do not call this on the UI thread or your app will crash.
  
  @param paymentIntentParams a set of params with which to confirm the Payment Intent
  @param publishableKey a publishable API key to use
  @return a {@link PaymentIntent} or {@code null} if a problem occurred
  
  @throws AuthenticationException
  @throws InvalidRequestException
  @throws APIConnectionException
  @throws APIException