* @since 10.0
   */
  @CanIgnoreReturnValue
  public static <K, V> ImmutableMap<K, V> uniqueIndex(
      Iterator<V> values, Function<? super V, K> keyFunction) {
    return uniqueIndex(values, keyFunction, ImmutableMap.builder());
  }

  private static <K, V> ImmutableMap<K, V> uniqueIndex(
      Iterator<V> values, Function<? super V, K> keyFunction, ImmutableMap.Builder<K, V> builder) {

   * @since 10.0
   */
  @CanIgnoreReturnValue
  public static <K, V> ImmutableMap<K, V> uniqueIndex(
      Iterator<V> values, Function<? super V, K> keyFunction) {
    return uniqueIndex(values, keyFunction, ImmutableMap.builder());
  }

  private static <K, V> ImmutableMap<K, V> uniqueIndex(
      Iterator<V> values, Function<? super V, K> keyFunction, ImmutableMap.Builder<K, V> builder) {

   * @since 14.0
   */
  @SuppressWarnings("nullness") // Unsafe, but we can't do much about it now.
  public final <K> ImmutableMap<K, @NonNull E> uniqueIndex(Function<? super E, K> keyFunction) {
    return Maps.uniqueIndex((Iterable<@NonNull E>) getDelegate(), keyFunction);
  }

  /**
   * Returns an array containing all of the elements from this fluent iterable in iteration order.
   *

   * @since 14.0
   */
  @SuppressWarnings("nullness") // Unsafe, but we can't do much about it now.
  public final <K> ImmutableMap<K, @NonNull E> uniqueIndex(Function<? super E, K> keyFunction) {
    return Maps.uniqueIndex((Iterable<@NonNull E>) getDelegate(), keyFunction);
  }

  /**
   * Returns an array containing all of the elements from this fluent iterable in iteration order.
   *