anchor.diff:    final double height;
     final EdgeInsets margin;
   
  -  final Function(Map<String, dynamic> result) onPaymentResult;
  -  final Function(Object? error)? onError;
  +  final void Function(Map<String, dynamic> result) onPaymentResult;
  +  final void Function(Object? error)? onError;
     final Widget? childOnError;
     final Widget? loadingIndicator;
   
  
positive.code:       builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.done) {
            if (snapshot.hasError) {
              widget.onError!(snapshot.error);
            }
  
            if (snapshot.data == true) {
  
negative.code:   }
  
    VoidCallback _defaultOnPressed(
        VoidCallback? onPressed, List<PaymentItem> paymentItems) {
      return () async {
        onPressed?.call();
        try {
          final result =
              await _payClient.showPaymentSelector(paymentItems: paymentItems);
          onPaymentResult(result);
        } catch (error) {
          onError?.call(error);
        }
      };
    }
  
    List<TargetPlatform> get _supportedPlatforms;
    Widget get _payButton;
  