js console.log json object could not get value by key

Question

This is My JavaScript code: a simple demo of Qweb template

<script src="./static/lib/jquery/jquery.js"></script>
<script type="text/javascript" src="qweb2.js"></script>

<script>
    QWeb = new QWeb2.Engine();
    QWeb.add_template('test.xml');

    console.log(QWeb);
    console.log(QWeb.templates);
    console.log('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa');

</script>

And here is the result in chrome console:

Why is console.log(Qweb.templates) returning an empty object?