NavigableSet<String> innerSet = new TreeSet<>();
                Collections.addAll(innerSet, elements);
                return Collections.unmodifiableNavigableSet(innerSet);
              }
            })
        .named("unmodifiableNavigableSet/TreeSet, natural")
        .withFeatures(
            CollectionFeature.KNOWN_ORDER,
            CollectionFeature.RESTRICTS_ELEMENTS,

          .put(ImmutableSet.class, ImmutableSet.of())
          .put(SortedSet.class, ImmutableSortedSet.of())
          .put(ImmutableSortedSet.class, ImmutableSortedSet.of())
          .put(NavigableSet.class, Sets.unmodifiableNavigableSet(Sets.newTreeSet()))
          .put(Map.class, ImmutableMap.of())
          .put(ImmutableMap.class, ImmutableMap.of())
          .put(SortedMap.class, ImmutableSortedMap.of())

          .put(ImmutableSet.class, ImmutableSet.of())
          .put(SortedSet.class, ImmutableSortedSet.of())
          .put(ImmutableSortedSet.class, ImmutableSortedSet.of())
          .put(NavigableSet.class, Sets.unmodifiableNavigableSet(Sets.newTreeSet()))
          .put(Map.class, ImmutableMap.of())
          .put(ImmutableMap.class, ImmutableMap.of())
          .put(SortedMap.class, ImmutableSortedMap.of())