code: public void changeSelected(String selectNode, ServletRequest request)
      {
          _selectedNode = TreeHelpers.changeSelected(this, _selectedNode, selectNode, request);
      }
docs: Change the node that is selected.  This is an optimization were the
  root node can track which node is currently selected so it can unselect
  that node instead of searching the whole tree to find the selected node.
  @param selectNode