How to capture the fields returned by the Checkout form in Razorpay in flutter

Question

My question is related to this link - https://razorpay.com/docs/payments/payment-gateway/flutter-integration/standard/build-integration/#19-store-fields-in-server

I need to capture the response of the checkout form in the flutter app but I am not able to understand what is the call which gets the response.

Is this a call that I need to make to the server or with the checkout form itself will give the response back?

I have had put the code like this, but the response is nowhere as shown in the documentation.

  var data = jsonDecode(response.body);
  print(data);
  await savepaymentData(data);
  openCheckout(amount, description, data["id"]);
  print(response.statusCode);
}
print('respsone body of the create order id');
print(response.body);

Any ideas.