TreeMultimap<@Nullable String, @Nullable Integer> multimap = createPopulate();
    assertThat(multimap.keySet()).containsExactly(null, "tree", "google").inOrder();
  }

  public void testOrderedAsMapEntries() {
    TreeMultimap<@Nullable String, @Nullable Integer> multimap = createPopulate();
    Iterator<Entry<String, Collection<Integer>>> iterator = multimap.asMap().entrySet().iterator();