* Future} need not be {@linkplain Future#isDone done}, making {@code AsyncFunction} suitable for
   * asynchronous derivations.
   *
   * <p>Throwing an exception from this method is equivalent to returning a failing {@code Future}.
   */
  ListenableFuture<O> apply(@ParametricNullness I input) throws Exception;

   * Future#isDone done}, making {@code AsyncCallable} suitable for asynchronous derivations.
   *
   * <p>Throwing an exception from this method is equivalent to returning a failing {@link
   * ListenableFuture}.
   */
  ListenableFuture<V> call() throws Exception;

   *     Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
   *         .collect(toImmutableSetMultimap(str -> str.charAt(0), str -> str.substring(1)));
   *
   * // is equivalent to
   *
   * static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
   *     new ImmutableSetMultimap.Builder<Character, String>()
   *         .put('b', "anana")
   *         .putAll('a', "pple", "sparagus")

  /**
   * Returns the empty iterator.
   *
   * <p>The {@link Iterable} equivalent of this method is {@link ImmutableSet#of()}.
   */
  static <T extends @Nullable Object> UnmodifiableIterator<T> emptyIterator() {
    return emptyListIterator();
  }

  /**
   * Returns the empty iterator.
   *
   * <p>The {@link Iterable} equivalent of this method is {@link ImmutableSet#of()}.
   */

   * the {@link Multimap} class documentation for clarification.
   */
  int size();

  /**
   * Returns {@code true} if this multimap contains no key-value pairs. Equivalent to {@code size()
   * == 0}, but can in some cases be more efficient.
   */
  boolean isEmpty();

  /**
   * Returns {@code true} if this multimap contains at least one key-value pair with the key {@code

    for (Cell<? extends R, ? extends C, ? extends V> cell : cells) {
      builder.put(cell);
    }
    return builder.buildOrThrow();
  }

  /**
   * Returns a new builder. The generated builder is equivalent to the builder created by the {@link
   * Builder#Builder() ImmutableTable.Builder()} constructor.
   */
  public static <R, C, V> Builder<R, C, V> builder() {
    return new Builder<>();
  }

  /**

  }

  protected void initMapWithNullKey() {
    resetMap(createArrayWithNullKey());
  }

  protected void initMapWithNullValue() {
    resetMap(createArrayWithNullValue());
  }

  /**
   * Equivalent to {@link #expectMissingKeys(Object[]) expectMissingKeys} {@code (null)} except that
   * the call to {@code contains(null)} is permitted to throw a {@code NullPointerException}.
   *

  /**
   * Not really a signature -- just the parts that affect whether one method is a fauxveride of a
   * method from an ancestor class.
   *
   * <p>See JLS 8.4.2 for the definition of the related "override-equivalent."
   */
  private static final class MethodSignature implements Comparable<MethodSignature> {
    final String name;
    final List<Class<?>> parameterTypes;
    final TypeSignature typeSignature;

    Entry<K, V>[] entries2 = (Entry<K, V>[]) entries;
    return copyOf(Arrays.asList(entries2));
  }

  /**
   * Returns a new builder. The generated builder is equivalent to the builder created by the {@link
   * Builder} constructor.
   */
  public static <K, V> Builder<K, V> builder() {
    return new Builder<>();
  }

  /**

   *     Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
   *         .collect(toImmutableSetMultimap(str -> str.charAt(0), str -> str.substring(1)));
   *
   * // is equivalent to
   *
   * static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
   *     new ImmutableSetMultimap.Builder<Character, String>()
   *         .put('b', "anana")
   *         .putAll('a', "pple", "sparagus")