code: function (items) {
          var self = this;
  
          self.items().set(self.create(items).concat(self.items().toArray()));
  
          return self.renderNew();
        }
docs: Prepends new instances to the current container.
  
  @method prepend
  @param {Array/tinymce.ui.Collection} items Array if controls to prepend.
  @return {tinymce.ui.Container} Current container instance.