docs: public void presentShippingFlow() {
          final Intent intent = new Intent(mHostActivity, PaymentFlowActivity.class)
                  .putExtra(PAYMENT_SESSION_CONFIG, mPaymentSessionConfig)
                  .putExtra(PAYMENT_SESSION_DATA_KEY, mPaymentSessionData)
                  .putExtra(EXTRA_PAYMENT_SESSION_ACTIVE, true);
          mHostActivity.startActivityForResult(intent, PAYMENT_SHIPPING_DETAILS_REQUEST);
      }