multimap.put("tree", 0);
    multimap.put("tree", null);
    return multimap;
  }

  /** Test that a TreeMultimap created from another uses the natural ordering. */
  public void testMultimapCreateFromTreeMultimap() {
    TreeMultimap<String, Integer> tree =
        TreeMultimap.create(StringLength.COMPARATOR, DECREASING_INT_COMPARATOR);
    tree.put("google", 2);
    tree.put("google", 6);
    tree.put("tree", 0);