Operator Overloading Javascript? (def.js)

Question

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Javascript syntax I haven’t seen till now, what does it do really?

Just saw http://github.com/tobeytailor/def.js today, and I don't understand how this works:

def ("Ninja") << Person ({
    init: function(name){
        this._super();
    },

    kick: function(){
        this.speak("I kick u!");
    }
});

Looking through the code for def.js, I don't see anything mentioning the << operator. How is this pseudo operator overloading happening?