MissingPluginException(No implementation found for method buildPayment Params on channel payumoney sdk) this is payumoney sdk problem

Question

This is flutter dependency error

error : MissingPluginException(No implementation found for method buildPayment Params on channel payumoney sdk)

This below code is payumoney default code i try this code with my key it's not working. for the security reason i can't share my key. payumoney account is free. anybody face this issue let me know please.

import 'package:flutter/material.dart';

import 'package:payumoney_sdk/payumoney_sdk.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  final payu = PayumoneySdk();

  @override
  void initState() {
    super.initState();
    startPayment();
  }

  void startPayment() async {
    final data = await payu.buildPaymentParams(
        amount: "400.0",
        transactionId: "C2161646224785587",
        phone: "7899395319",
        productInfo: "Nike shoes",
        firstName: "Badal Sharma",
        email: "[email protected]",
        hash: "2973e780893f5b3ff593cf92891a3763f20a9fb55c84c734d4e317727b75ccbae45d9f0da97e28c4521c03c144335c082c8b6045a296dccb24d1f5bc5063afd9",
        isProduction: false,
        userCredentials: "7899395319",
        merchantKey: "mWI8Vl",
        salt: "cMDID7EG",
        merchantName: "Siply Services Pvt Ltd."
    );


  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Payumoney SDK'),
        ),
        body: Center(
          child: Column(
            children: [
              SizedBox(
                height: 100,
              ),
              TextButton(
                  onPressed: () {
                    startPayment();
                  },
                  child: Text("Tap me"))
            ],
          ),
        ),
      ),
    );
  }
}