define(function(require) {
  var Marionette = require('marionette');

  // ... Other related stuff ...

  return Marionette.CollectionView.extend({
    childView: GroupItemView,
    collection: new MyCollection(),

    initialize: function() {
      this.collection.fetch();

      this.on('render:collection', this.onCollectionRendered);
    },

    onRender: function() {
      alert('onRender');
    },

    onCollectionRendered: function() {
      alert('onCollectionRendered');
    }

  });

});