code: function (items) {
          var self = this, parent = self.parent();
  
          if (parent) {
            parent.insert(items, parent.items().indexOf(self), true);
          }
  
          return self;
        }
docs: Adds items before the current control.
  
  @method before
  @param {Array/tinymce.ui.Collection} items Array of items to prepend before this control.
  @return {tinymce.ui.Control} Current control instance.