The method 'FlatButton' isn't defined for the class '_MollieCheckoutState'.

[bassim]

../../.pub-cache/hosted/pub.dev/fluttermollie-0.8.11/lib/src/molliecheckout.dart:105:20: Error: The method 'FlatButton' isn't defined for the class '_MollieCheckoutState'.
 - '_MollieCheckoutState' is from 'package:fluttermollie/src/molliecheckout.dart' ('../../.pub-cache/hosted/pub.dev/fluttermollie-0.8.11/lib/src/molliecheckout.dart').
Try correcting the name to the name of an existing method, or defining a method named 'FlatButton'.
            child: FlatButton(
                   ^^^^^^^^^^

I think FlatButton is no longer available? Using flutter 3.7.6