return builder.build();
  }

  /**
   * Returns an immutable multimap containing the given entries, in order. Repeated occurrences of
   * an entry (according to {@link Object#equals}) after the first are ignored.
   */
  public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1, K k2, V v2) {
    ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
    builder.put(k1, v1);
    builder.put(k2, v2);

   * the first are ignored.
   */
  public static <E> ImmutableSet<E> of(E e1, E e2) {
    return construct(2, e1, e2);
  }

  /**
   * Returns an immutable set containing the given elements, minus duplicates, in the order each was
   * first specified. That is, if multiple elements are {@linkplain Object#equals equal}, all except
   * the first are ignored.
   */

  }

  private static void writeSelfReferencingJarFile(File jarFile, String... entries)
      throws IOException {
    Manifest manifest = new Manifest();
    // Without version, the manifest is silently ignored. Ugh!
    manifest.getMainAttributes().put(Attributes.Name.MANIFEST_VERSION, "1.0");
    manifest.getMainAttributes().put(Attributes.Name.CLASS_PATH, jarFile.getName());

    Closer closer = Closer.create();
    try {

   * all elements that are contained by {@code set1} and not contained by {@code set2}. {@code set2}
   * may also contain elements not present in {@code set1}; these are simply ignored. The iteration
   * order of the returned set matches that of {@code set1}.
   *
   * <p>Results are undefined if {@code set1} and {@code set2} are sets based on different

    }
  }

  /** Waiter links form a Treiber stack, in the {@link #waiters} field. */
  private static final class Waiter {
    static final Waiter TOMBSTONE = new Waiter(false /* ignored param */);

    @CheckForNull volatile Thread thread;
    @CheckForNull volatile Waiter next;

    /**
     * Constructor for the TOMBSTONE, avoids use of ATOMIC_HELPER in case this class is loaded

          throw multiples(true);
        }
        return this;
      }
    }

    @IgnoreJRERequirement // see enclosing class (whose annotation Animal Sniffer ignores here...)
    Optional<Object> getOptional() {
      if (extras.isEmpty()) {
        return Optional.ofNullable(element);
      } else {
        throw multiples(false);
      }
    }

  }

  // TODO: Re-enable this test after moving to new serialization format in ImmutableMap.
  @J2ktIncompatible
  @GwtIncompatible // SerializableTester
  @SuppressWarnings("unchecked")
  public void ignore_testSerializationNoDuplication_regularImmutableMap() throws Exception {
    // Tests that serializing a map, its keySet, and values only writes the underlying data once.

    Object[] entries = new Object[2000];

     *     null arguments
     */
    @ParametricNullness
    V2 transformEntry(@ParametricNullness K key, @ParametricNullness V1 value);
  }

  /** Views a function as an entry transformer that ignores the entry key. */
  static <K extends @Nullable Object, V1 extends @Nullable Object, V2 extends @Nullable Object>
      EntryTransformer<K, V1, V2> asEntryTransformer(final Function<? super V1, V2> function) {