private void toggleExpansion(TreePath path) {
    if (path == null) {
      return;
    }

    if (getTreeStep().isSelectable(path.getLastPathComponent(), extractUserObject(path.getLastPathComponent()))) {
      if (myWizardTree.isExpanded(path)) {
        myWizardTree.collapsePath(path);
      }
      else {
        myWizardTree.expandPath(path);
      }
    }
  }
private void toggleExpansion(TreePath path)