Creating associations between lists and todos in Backbone.js

todolists.js

var TodoLists = Backbone.Collection.extend({
    model: TodoList
});
 
var TodoList = Backbone.Model.extend({
    defaults: {
        name: ''
    },
    
    initialize: function(options) {
        this.collection = options.collection;
    }
});
 
var TodoCollection = Backbone.Collection.extend({
    model: Todo
});
 
var Todo = Backbone.Model.extend({
    defaults: {
        text: '',
        finished: false,
        due_date: null
    }
});
 
 
 
 
var collection = new TodoCollection([{text: 'item one'}, {text: 'item two'}]);
var list = new TodoList({
    name: 'My List'
    collection: collection
});
 
var collection2 = new TodoCollection([{text: 'item three'}, {text: 'item four'}]);
var list2 = new TodoList({
    name: 'My Other List',
    collection: collection2
});
 
 
var lists = new TodoLists([list, list2]);