Interesting way to inject underscore into Angular.js

gistfile1.txt

var underscore = angular.module('underscore', []);
underscore.factory('_', function() { 
    return window._; //Underscore must already be loaded on the page 
});

app.controller('MainCtrl', ['$scope', '_', function($scope, _) { 
    init = function() { 
        _.keys($scope);
    } 
    init();
}]);