docs: function tabBrowser_getTabPanelElement(tabIndex, elemString)
    {
      var index = tabIndex ? tabIndex : this.selectedIndex;
      var elemStr = elemString ? elemString : "";
  
      // Get the tab panel and check if an element has to be fetched
      var panel = this.getElement({type: "tabs_tabPanel", subtype: "tab", value: this.getTab(index)});
      var elem = new elementslib.Lookup(this._controller.window.document, panel.expression + elemStr);
  
      return elem;
    }