context : context in Alert(); is throwing an error

I'm new to Flutter . Any help is appreciated. Thanks in advance. The error is : Undefined name 'context'. Try correcting the name to one that is defined, or defining the name. Here's my code :
import 'package:flutter/material.dart';
import 'package:quizzler/quiz_brain.dart';
import 'package:rflutter_alert/rflutter_alert.dart';

void main() => runApp(Quizzler());

class Quizzler extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        backgroundColor: Colors.grey.shade900,
        body: SafeArea(
          child: Padding(
            padding: EdgeInsets.symmetric(horizontal: 10.0),
            child: QuizPage(),
          ),
        ),
      ),
    );
  }
}

List<Icon> scoreKeeper = [];

void checkUserAnswer(bool userPickedAnswer) {
  bool correctAnswer = quizBrain.getQuestionAnswer();
//TODO: Step 4 - Use IF/ELSE to check if we've reached the end of the quiz. If true, execute Part A, B, C, D.
  //TODO: Step 4 Part A - show an alert using rFlutter_alert (remember to read the docs for the package!)
  //HINT! Step 4 Part B is in the quiz_brain.dart
  //TODO: Step 4 Part C - reset the questionNumber,
  //TODO: Step 4 Part D - empty out the scoreKeeper.

  //TODO: Step 5 - If we've not reached the end, ELSE do the answer checking steps below

  if (quizBrain.isFinished() == true) {
    Alert(
      context: context,
      type: AlertType.error,
      title: "RFLUTTER ALERT",
      desc: "Flutter is more awesome with RFlutter Alert.",
      buttons: [
        DialogButton(
          child: Text(
            "COOL",
            style: TextStyle(color: Colors.white, fontSize: 20),
          ),
          onPressed: () => Navigator.pop(context),
          width: 120,
        )
      ],
    ).show();
    quizBrain.reset();
    scoreKeeper = [];
  } else {
    if (correctAnswer == userPickedAnswer) {
      scoreKeeper.add(Icon(
        Icons.check,
        color: Colors.green,
      ));
    } else {
      scoreKeeper.add(Icon(
        Icons.close,
        color: Colors.red,
      ));
    }
    quizBrain.nextQuestion();
  }

  //The user picked true.
}
// List<String> questions = [
//   'You can lead a cow down stairs but not up stairs.',
//   'Approximately one quarter of human bones are in the feet.',
//   'A slug\'s blood is green.'
// ];
// List<bool> answers = [
//   false,
//   true,
//   true,
// ];

// List<Question> questionBank = [
//   Question(q: 'You can lead a cow down stairs but not up stairs.', a: false),
//   Question(
//       q: 'Approximately one quarter of human bones are in the feet.', a: true),
//   Question(q: 'A slug\'s blood is green.', a: true),
// ];

QuizBrain quizBrain = QuizBrain();

class QuizPage extends StatefulWidget {
  @override
  _QuizPageState createState() => _QuizPageState();
}

class _QuizPageState extends State<QuizPage> {
  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.spaceBetween,
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: <Widget>[
        Expanded(
          flex: 5,
          child: Padding(
            padding: EdgeInsets.all(10.0),
            child: Center(
              child: Text(
                quizBrain.getQuestionText(),
                textAlign: TextAlign.center,
                style: TextStyle(
                  fontSize: 25.0,
                  color: Colors.white,
                ),
              ),
            ),
          ),
        ),
        Expanded(
          child: Padding(
            padding: EdgeInsets.all(15.0),
            child: FlatButton(
              textColor: Colors.white,
              color: Colors.green,
              child: Text(
                'True',
                style: TextStyle(
                  color: Colors.white,
                  fontSize: 20.0,
                ),
              ),
              onPressed: () {
                setState(() {
                  checkUserAnswer(true);
                });
              },
            ),
          ),
        ),
        Expanded(
          child: Padding(
            padding: EdgeInsets.all(15.0),
            child: FlatButton(
              color: Colors.red,
              child: Text(
                'False',
                style: TextStyle(
                  fontSize: 20.0,
                  color: Colors.white,
                ),
              ),
              onPressed: () {
                //The user picked false.
                setState(() {
                  checkUserAnswer(false);
                });
              },
            ),
          ),
        ),
        //TODO: Add a Row here as your score keeper
        //TODO: This is how u create a to do
        Expanded(
          child: Row(
            children: scoreKeeper,
          ),
        )
      ],
    );
  }
}

/*
question1: 'You can lead a cow down stairs but not up stairs.', false,
question2: 'Approximately one quarter of human bones are in the feet.', true,
question3: 'A slug\'s blood is green.', true,
*/
RatelHub / rflutter_alert

context : context in Alert(); is throwing an error #88
