uniqueIndex(
          Iterables.<MapsImplEnum>concat(
              asList(MapImpl.values()), asList(SortedMapImpl.values()), asList(BiMapImpl.values())),
          toStringFunction());

  @Param({
    "HashMapImpl",
    "LinkedHashMapImpl",
    "ConcurrentHashMapImpl",
    "CompactHashMapImpl",
    "CompactLinkedHashMapImpl",
    "ImmutableMapImpl",
    "TreeMapImpl",
    "ImmutableSortedMapImpl",