Backbone - Relational Nested working without KeySources

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/backbone.js/1.3.3/backbone-min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/backbone-localstorage.js/1.1.16/backbone.localStorage-min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/backbone-relational/0.10.0/backbone-relational.min.js"></script>
<html>
<head>
</head>
<body>
</body>
</html>

JavaScript

modelA = Backbone.RelationalModel.extend({
    defaults: {
        name: "modelA",
    },
    relations: [
        {
        type: Backbone.HasMany,
        key: 'model_bs',
        relatedModel: 'modelB',
        collectionType: 'modelBs',
        reverseRelation: {
            key: 'model_a',
            includeInJSON: 'id'
        }}
    ]
});

modelB = Backbone.RelationalModel.extend({
    defaults: {
        name: "modelB",
    },
    relations: [
        {
        type: Backbone.HasMany,
        key: 'model_cs',
        relatedModel: 'modelC',
        collectionType: 'modelCs',
        reverseRelation: {
            key: 'model_b',
            includeInJSON: 'id'
        }}
    ]
});

modelC = Backbone.RelationalModel.extend({
    defaults: {
        name: "modelC",
    },
});

modelAs = Backbone.Collection.extend({
    model: modelA,
    localStorage: new Store("modelAs")
});
modelBs = Backbone.Collection.extend({
    model: modelB,
    localStorage: new Store("modelBs")
});
modelCs = Backbone.Collection.extend({
    model: modelC,
    localStorage: new Store("modelCs")
});

preLoadAs = [
    {
    id: 1,
    name: 'Aone',
    model_bs: [1, 2, 3]},
{
    id: 2,
    name: 'Atwo'},
{
    id: 3,
    name: 'Athree'},
    ]

preLoadBs = [
    {
    id: 1,
    name: 'Bone',
    model_cs: [1, 2, 3],
    model_a_id: 1},
{
    id: 2,
    name: 'Btwo',
    model_a_id: 1},
{
    id: 3,
    name: 'Bthree',
    model_a_id: 1},
    ]

preLoadCs = [
    {
    id: 1,
    name: 'Cone',
    model_c_id: 1},
{
    id: 2,
    name: 'Ctwo',
    model_c_id: 1},
{
    id: 3,
    name: 'Cthree',
    model_c_id: 1},
    ]

loaderA = new modelAs();
loaderA.reset(preLoadAs);

loaderB = new modelBs();
loaderB.reset(preLoadBs);

loaderC = new modelCs();
loaderC.reset(preLoadCs);

testAs = new modelAs();
testAs.reset(preLoadAs);

testA = testAs.get(1);
$("body").append("Test A: ");
$("body").append(testA.get('name'));
$("body").append("<br/>");

testA.getAsync('model_bs');
testBs =...