* 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.)
   *

   * copy.
   *
   * <p><b>Warning:</b> {@code keyPredicate} 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.
   *
   * @since 11.0
   */

    }
    return builder.append("]").toString();
  }

  /**
   * Provide a human-readable explanation of why this future has not yet completed.
   *
   * @return null if an explanation cannot be provided (e.g. because the future is done).
   * @since 23.0
   */
  @CheckForNull
  protected String pendingToString() {

    implements NavigableMap<K, V> {
  /**
   * Returns a {@link Collector} that accumulates elements into an {@code ImmutableSortedMap} whose
   * keys and values are the result of applying the provided mapping functions to the input
   * elements. The generated map is sorted by the specified comparator.
   *
   * <p>If the mapped keys contain duplicates (according to the specified comparator), an {@code

  }

  public void testPowerSetIteration_manual() {
    ImmutableSet<Integer> elements = ImmutableSet.of(1, 2, 3);
    Set<Set<Integer>> powerSet = powerSet(elements);
    // The API doesn't promise this iteration order, but it's convenient here.
    Iterator<Set<Integer>> i = powerSet.iterator();
    assertEquals(ImmutableSet.of(), i.next());
    assertEquals(ImmutableSet.of(1), i.next());

  }

  // Constructors

  /**
   * Constructor for use by subclasses. When subclassing, you may want to override {@code
   * toString()} to provide a useful description.
   */
  protected CharMatcher() {}

  // Abstract methods

  /** Determines a true or false value for the given character. */
  public abstract boolean matches(char c);

  }

  // Constructors

  /**
   * Constructor for use by subclasses. When subclassing, you may want to override {@code
   * toString()} to provide a useful description.
   */
  protected CharMatcher() {}

  // Abstract methods

  /** Determines a true or false value for the given character. */
  public abstract boolean matches(char c);

    implements NavigableMap<K, V> {
  /**
   * Returns a {@link Collector} that accumulates elements into an {@code ImmutableSortedMap} whose
   * keys and values are the result of applying the provided mapping functions to the input
   * elements. The generated map is sorted by the specified comparator.
   *
   * <p>If the mapped keys contain duplicates (according to the specified comparator), an {@code

   * failed future if any of the items fails.
   *
   * <p>Canceling this future will attempt to cancel all the component futures, and if any of the
   * provided futures fails or is canceled, this one is, too.
   *
   * @param futures futures to combine
   * @return a future that provides a list of the results of the component futures
   * @since 10.0
   */
  @SafeVarargs

    // Convenience methods for testing

    /**
     * Unsafe cast of the given entry to {@code E}, the type of the specific {@link InternalEntry}
     * implementation type.
     *
     * <p>This method is provided as a convenience for tests. Otherwise they'd need to be
     * knowledgeable about all the implementation details of our type system trickery.
     */
    abstract E castForTesting(InternalEntry<K, V, ?> entry);