*
   * <p>The returned object is serializable if this object is serializable.
   *
   * @since 10.0
   */
  @GwtCompatible(serializable = true)
  public final <S extends @Nullable T> Equivalence<Iterable<S>> pairwise() {
    // Ideally, the returned equivalence would support Iterable<? extends T>. However,
    // the need for this is so rare that it's not worth making callers deal with the ugly wildcard.

 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public final class Comparators {
  private Comparators() {}

  /**
   * Returns a new comparator which sorts iterables by comparing corresponding elements pairwise
   * until a nonzero result is found; imposes "dictionary order." If the end of one iterable is
   * reached, but not the other, the shorter iterable is considered to be less than the longer one.

            Comparator.naturalOrder(), Entry::getKey, Entry::getValue, Integer::sum);
    Equivalence<ImmutableMap<String, Integer>> equivalence =
        Equivalence.equals().<Entry<String, Integer>>pairwise().onResultOf(ImmutableMap::entrySet);
    CollectorTester.of(collector, equivalence)
        .expectCollects(
            ImmutableSortedMap.of("one", 1, "three", 3, "two", 4),
            mapEntry("one", 1),

        ImmutableBiMap.toImmutableBiMap(Entry::getKey, Entry::getValue);
    Equivalence<ImmutableBiMap<String, Integer>> equivalence =
        Equivalence.equals()
            .<Entry<String, Integer>>pairwise()
            .onResultOf(ImmutableBiMap::entrySet);
    CollectorTester.of(collector, equivalence)
        .expectCollects(
            ImmutableBiMap.of("one", 1, "two", 2, "three", 3),
            mapEntry("one", 1),

      Iterable<? extends Comparator<? super T>> comparators) {
    return new CompoundOrdering<>(comparators);
  }

  /**
   * Returns a new ordering which sorts iterables by comparing corresponding elements pairwise until
   * a nonzero result is found; imposes "dictionary order". If the end of one iterable is reached,
   * but not the other, the shorter iterable is considered to be less than the longer one. For