code: function () {
          var self = this, layout = self._layout;
  
          self.classes.add('btn-group');
          self.preRender();
          layout.preRender(self);
  
          return (
            '<div id="' + self._id + '" class="' + self.classes + '">' +
            '<div id="' + self._id + '-body">' +
            (self.settings.html || '') + layout.renderHtml(self) +
            '</div>' +
            '</div>'
          );
        }
docs: Renders the control as a HTML string.
  
  @method renderHtml
  @return {String} HTML representing the control.