public CheckedTreeNode append(CheckedTreeNode node) {
   if (!myGroupByClasses) {
     return node;
   }
   final TreeDescriptor descriptor = getDescriptor(node);
   if (!(descriptor instanceof MethodDescriptor)) {
     return node;
   }
   final MethodDescriptor methodDescriptor = (MethodDescriptor) descriptor;
   final String className = methodDescriptor.getClassName();
   final String packageName = methodDescriptor.getPackageName();
   return attachNodeToParent(new ClassDescriptor(className, packageName), node);
 }