overrid compar object obj object obj obj mutabl tree node mutabl tree node node mutabl tree node obj obj node user object obj mutabl tree node mutabl tree node node mutabl tree node obj obj node user object obj obj obj type obj type obj diagram type treat equal issu type index diagram type index diagram compar user object obj obj type order type compar type type order compar user object obj obj type index diagram type index diagram type index diagram type index diagram type index type index type index type index type order 