code: function($el, newView, options) {
        var currentDeferred = $.Deferred(),
          parentView = this;
        options = _.extend({}, options);
        _.defaults(options, {
          parentView: this,
          newView: newView
        });
        newView.transitionIn(function() {
          parentView.attachView($el, newView, options);
        }, currentDeferred.resolve, options);
        return currentDeferred.promise();
      }
docs: Simliar to this.attachView except it utilizes the new view's transitionIn method instead of just attaching the view.
  This method is invoked on the parent view to attach a tracked view where the transitionIn method defines how a tracked view is brought onto the page.
  @param $el {jQuery element} the element to attach to.
  @param newView {View} the view to be transitioned in.
  @param [options] {Object} optional options object
  @param   [options.noActivate=false] {Boolean} if set to true, the view will not be activated upon attaching.
  @param   [options.shared=false] {Boolean} if set to true, the view will be treated as a shared view and not disposed during parent view disposing.
  @return {Promise} resolved when transition is complete. No payload is provided upon resolution.
  @method transitionInView
  @private