Используя shim by requirejs2, есть ли способ сказать, требует ли модуль уже загружен?

Пример:

<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript" src="undescrore.js"></script>
<script type="text/javascript" src="require.js'"></script>
<script type="text/javascript">
    require.config({
        paths: {
            "backbone": '/vendor/js/backbone-min.js'
        },
        shim: {
            'backbone': {
                //These script dependencies should be loaded before loading
                //backbone.js
                deps: ['underscore', 'jquery'], // here I would like to load the already loaded library
            }
        }
    });
</script>