"Undefined is not a function" error when calling a Backbone collection's fetch function

I am getting an error when calling the fetch function.

Undefined is not a function Error in Backbone js 

var models = Backbone.Model.extend({
  userId: function() {
    return this.get('userId');
  },
  id: function() {
    return this.get('id');
  },
  body: function() {
    return this.get('body');
  }
});
//Collections
var todolistStore = Backbone.Collection.extend({
  url: function() {
    return 'https://jsonplaceholder.typicode.com/posts'
  },
  model: models,
  parse: function(response) {
    return response;
  }
});
todolistStore.fetch();

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://ajax.cdnjs.com/ajax/libs/underscore.js/1.1.4/underscore-min.js" type="text/javascript"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/backbone.js/0.9.2/backbone-min.js" type="text/javascript"></script>

There are a couple of problems. I'm building off of @ChrisG 's answer.

1. You need to instantiate a collection. Here's what my code:

   var Model = Backbone.Model.extend({
       userId: function() {
           return this.get('userId');
       },
       id: function() {
           return this.get('id');
       },
       body: function() {
           return this.get('body');
       }
   });
   
   //Collections
   var TodoListStore = Backbone.Collection.extend({
       url: function() {
           return 'https://jsonplaceholder.typicode.com/posts'
       },
       model: Model,
       parse: function(response) {
           return response;
       }
   });
   
   var todolistStore = new TodoListStore();
   todolistStore.fetch();
   

2. I updated the version of Underscore and Backbone

   https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js https://cdnjs.cloudflare.com/ajax/libs/backbone.js/1.3.3/backbone-min.js