!item.equals(NotAnInstance.EQUAL_TO_NOTHING));
      assertTrue(item + " must be Object#equals to itself", item.equals(item));
      assertEquals(
          "the Object#hashCode of " + item + " must be consistent",
          item.hashCode(),
          item.hashCode());
      if (!(item instanceof String)) {
        assertTrue(
            item + " must not be Object#equals to its Object#toString representation",

   * predicate)} and use the copy.
   *
   * <p><b>Warning:</b> {@code predicate} must be <i>consistent with equals</i>, as documented at
   * {@link Predicate#apply}. Do not provide a predicate such as {@code
   * Predicates.instanceOf(ArrayList.class)}, which is inconsistent with equals. (See {@link
   * Iterables#filter(Iterable, Class)} for related functionality.)
   *

  }

  @Override
  public int hashCode() {
    return Sets.hashCodeImpl(this);
  }

  // This declaration is needed to make Set.iterator() and
  // ImmutableCollection.iterator() appear consistent to javac's type inference.
  @Override
  public abstract UnmodifiableIterator<E> iterator();

  abstract static class CachingAsList<E> extends ImmutableSet<E> {
    @LazyInit private transient ImmutableList<E> asList;

   * lesser. For example, {@code [] < [1.0f] < [1.0f, 2.0f] < [2.0f]}.
   *
   * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
   * support only identity equality), but it is consistent with {@link Arrays#equals(float[],
   * float[])}.
   *
   * @since 2.0
   */
  public static Comparator<float[]> lexicographicalComparator() {

 * {@code equals} would break symmetry, as the forwarding object might consider itself equal to the
 * object being tested, but the reverse could not be true. This behavior is consistent with the
 * JDK's collection wrappers, such as {@link java.util.Collections#unmodifiableCollection}. Use an
 * interface-specific subclass of {@code ForwardingObject}, such as {@link ForwardingList}, to

  /**
   * Returns a view of the entries stored in this cache as a thread-safe map. Modifications made to
   * the map directly affect the cache.
   *
   * <p>Iterators from the returned map are at least <i>weakly consistent</i>: they are safe for
   * concurrent use, but if the cache is modified (including by eviction) after the iterator is
   * created, it is undefined which of the changes (if any) will be reflected in that iterator.
   */

      assertTrue(item + " must be equivalent to itself", equivalence.equivalent(item, item));
      assertEquals(
          "the hash of " + item + " must be consistent",
          equivalence.hash(item),
          equivalence.hash(item));
    }
  }

 * {@link Comparator#compare} instead of {@link Object#equals} to determine equivalence of
 * instances.
 *
 * <p><b>Warning:</b> The comparators or comparables used must be <i>consistent with equals</i> as
 * explained by the {@link Comparable} class specification. Otherwise, the resulting multiset will
 * violate the general contract of {@link SetMultimap}, which is specified in terms of {@link
 * Object#equals}.

   */
  public abstract N target();

  /**
   * If this {@link EndpointPair} {@link #isOrdered()} returns the {@link #source()}; otherwise,
   * returns an arbitrary (but consistent) endpoint of the origin edge.
   */
  public final N nodeU() {
    return nodeU;
  }

  /**
   * Returns the node {@link #adjacentNode(Object) adjacent} to {@link #nodeU()} along the origin

   * expected</i>, but not absolutely required, to have the following properties:
   *
   * <ul>
   *   <li>Its execution does not cause any observable side effects.
   *   <li>The computation is <i>consistent with equals</i>; that is, {@link Objects#equal
   *       Objects.equal}{@code (a, b)} implies that {@code Objects.equal(function.apply(a),
   *       function.apply(b))}.
   * </ul>
   *