*
   *   private static final class FooFactoryForTest {
   *     public static Foo create(String a, String b, int c, boolean d) {
   *       return Foo.builder()
   *           .setA(a)
   *           .setB(b)
   *           .setC(c)
   *           .setD(d)
   *           .build();
   *     }
   *   }
   *
   *   public void testEquals() {
   *     new ClassSanityTester()

   *
   * <p>Results are undefined if {@code set1} and {@code set2} are sets based on different
   * equivalence relations, for example if {@code set1} is a {@link HashSet} and {@code set2} is a
   * {@link TreeSet} or the {@link Map#keySet} of an {@code IdentityHashMap}.
   */
  public static <E extends @Nullable Object> SetView<E> difference(Set<E> set1, Set<?> set2) {
    checkNotNull(set1, "set1");
    checkNotNull(set2, "set2");

    assertTrue(set.containsAll(Sets.newTreeSet(asList("a", "b", "f"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("d"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("z"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("b", "d"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("f", "d", "a"))));
  }

    assertTrue(set.containsAll(Sets.newTreeSet()));
    assertTrue(set.containsAll(Sets.newTreeSet(asList("b"))));
    assertTrue(set.containsAll(Sets.newTreeSet(asList("a", "f"))));
    assertTrue(set.containsAll(Sets.newTreeSet(asList("a", "b", "f"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("d"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("z"))));

    BiPredicate<ImmutableSet<TypeWithDuplicates>, ImmutableSet<TypeWithDuplicates>> equivalence =
        (set1, set2) -> {
          if (!set1.equals(set2)) {
            return false;
          }
          for (int i = 0; i < set1.size(); i++) {
            if (!set1.asList().get(i).fullEquals(set2.asList().get(i))) {
              return false;
            }
          }
          return true;
        };

  private Iterable<List<Object>> buildCartesianProduct(Set<?>... sets) {
    List<Set<Optional<?>>> optionalSets = Lists.newArrayListWithExpectedSize(sets.length);
    for (Set<?> set : sets) {
      Set<Optional<?>> optionalSet =
          Sets.newLinkedHashSet(Iterables.transform(set, Optional::fromNullable));
      optionalSets.add(optionalSet);
    }
    Set<List<Optional<?>>> cartesianProduct = Sets.cartesianProduct(optionalSets);

  /**
   * Returns a {@link Set} whose methods throw {@link IllegalStateException} when the given node is
   * not present in this network.
   *
   * @since 33.1.0
   */
  protected final <T> Set<T> nodeInvalidatableSet(Set<T> set, N node) {
    return InvalidatableSet.of(
        set, () -> nodes().contains(node), () -> String.format(NODE_REMOVED_FROM_GRAPH, node));
  }

  /**

      Set<K> set, Function<? super K, V> function) {
    return new AsMapView<>(set, function);
  }

  /**
   * Returns a view of the sorted set as a map, mapping keys from the set according to the specified
   * function.
   *
   * <p>Specifically, for each {@code k} in the backing set, the returned map has an entry mapping

      Set<K> set, Function<? super K, V> function) {
    return new AsMapView<>(set, function);
  }

  /**
   * Returns a view of the sorted set as a map, mapping keys from the set according to the specified
   * function.
   *
   * <p>Specifically, for each {@code k} in the backing set, the returned map has an entry mapping

     *
     * @return the highlighting type
     */
    public String getType() {
        return type;
    }

    /**
     * Sets the highlighting type with fluent interface.
     *
     * @param type the highlighting type to set
     * @return this HighlightInfo instance for method chaining
     */
    public HighlightInfo type(final String type) {
        this.type = type;
        return this;