How to use pc.ModelHandler to change the default material for all imported models?

I think it is a good idea to automate materials creation for all imported 3d models.
I am using the GLB utility to import models and I don’t really need this feature in the editor, but how to implement it in my scripts?
I can create the new handler this way:

UrlLoader.prototype.initialize = function() {    
    var new_handler = new pc.ModelHandler(, new pc.BasicMaterial());
//what is next?

How to use new_handler?