`if obj.model === view` suggests that the `view` variable actually represents a model, in which case you should be using the `findByModel` method instead of this one.  However, I don't think that `getListItemIndex` should take a model, I think it should take a view.  If it takes a view, then this method turns into a simple indexOf, which underscore provides.

Check out how we mixin underscore methods here: https://github.com/zmetcalf/django-widgy/blob/b94d1e81e643f40e4e06008f28d2d2807d3e967b/widgy/static/widgy/js/widgy.backbone.js#L235-L244