*     keyFunction} on each value in the input collection to that value
   * @throws NullPointerException if any element of {@code values} is {@code null}, or if {@code
   *     keyFunction} produces {@code null} for any key
   */
  public static <K, V> ImmutableListMultimap<K, V> index(
      Iterable<V> values, Function<? super V, K> keyFunction) {
    return index(values.iterator(), keyFunction);
  }

   *     in the input collection to that value
   * @throws IllegalArgumentException if {@code keyFunction} produces the same key for more than one
   *     value in the input collection
   * @throws NullPointerException if any element of {@code values} is {@code null}, or if {@code
   *     keyFunction} produces {@code null} for any value
   */
  @CanIgnoreReturnValue
  public static <K, V> ImmutableMap<K, V> uniqueIndex(

   *
   * <p><b>Performance note:</b> the instance returned is a singleton.
   */
  @SuppressWarnings({"unchecked"}) // fully variant implementation (never actually produces any Es)
  public static <E> ImmutableSet<E> of() {
    return (ImmutableSet<E>) RegularImmutableSet.EMPTY;
  }

  /**
   * Returns an immutable set containing {@code element}. Preferred over {@link

   *     is greater than the number of elements remaining in {@code iterator}
   * @return the element at the specified position in {@code iterator} or {@code defaultValue} if
   *     {@code iterator} produces fewer than {@code position + 1} elements.
   * @throws IndexOutOfBoundsException if {@code position} is negative
   * @since 4.0
   */
  @ParametricNullness
  public static <T extends @Nullable Object> T get(