Function<? super T, ? extends K> keyFunction,
          Function<? super T, ? extends V> valueFunction,
          BinaryOperator<V> mergeFunction) {
    checkNotNull(comparator);
    checkNotNull(keyFunction);
    checkNotNull(valueFunction);
    checkNotNull(mergeFunction);
    return Collectors.collectingAndThen(
        Collectors.toMap(
            keyFunction, valueFunction, mergeFunction, () -> new TreeMap<K, V>(comparator)),

   */
  public static <T extends @Nullable Object> Iterable<T> filter(
      final Iterable<T> unfiltered, final Predicate<? super T> retainIfTrue) {
    checkNotNull(unfiltered);
    checkNotNull(retainIfTrue);
    return new FluentIterable<T>() {
      @Override
      public Iterator<T> iterator() {
        return Iterators.filter(unfiltered.iterator(), retainIfTrue);
      }
    };

  private final Random random;

  public RandomAmountInputStream(InputStream in, Random random) {
    super(checkNotNull(in));
    this.random = checkNotNull(random);
  }

  @Override
  public int read(byte[] b, int off, int len) throws IOException {
    return super.read(b, off, random.nextInt(len) + 1);
  }

  final Multimap<K, V> unfiltered;
  final Predicate<? super K> keyPredicate;

  FilteredKeyMultimap(Multimap<K, V> unfiltered, Predicate<? super K> keyPredicate) {
    this.unfiltered = checkNotNull(unfiltered);
    this.keyPredicate = checkNotNull(keyPredicate);
  }

  @Override
  public Multimap<K, V> unfiltered() {
    return unfiltered;
  }

  @Override
  public Predicate<? super Entry<K, V>> entryPredicate() {

   * the behavior of this method is undefined but we make a reasonable effort at converting anyway.
   */
  public final String to(CaseFormat format, String str) {
    checkNotNull(format);
    checkNotNull(str);
    return (format == this) ? str : convert(format, str);
  }

  /** Enum values can override for performance reasons. */
  String convert(CaseFormat format, String s) {

    UncheckedThrowingFuture<V> future = new UncheckedThrowingFuture<V>();
    future.complete(checkNotNull(error));
    return future;
  }

  public static <V> ListenableFuture<V> throwingRuntimeException(RuntimeException e) {
    UncheckedThrowingFuture<V> future = new UncheckedThrowingFuture<V>();
    future.complete(checkNotNull(e));
    return future;
  }

  public static <V> UncheckedThrowingFuture<V> incomplete() {

  public static final <E> InvalidatableSet<E> of(
      Set<E> delegate, Supplier<Boolean> validator, Supplier<String> errorMessage) {
    return new InvalidatableSet<>(
        checkNotNull(delegate), checkNotNull(validator), checkNotNull(errorMessage));
  }

  @Override
  protected Set<E> delegate() {
    validate();
    return delegate;
  }

  private InvalidatableSet(

  }

  @Override
  public boolean hasEdgeConnecting(N nodeU, N nodeV) {
    return hasEdgeConnectingInternal(checkNotNull(nodeU), checkNotNull(nodeV));
  }

  @Override
  public boolean hasEdgeConnecting(EndpointPair<N> endpoints) {
    checkNotNull(endpoints);
    return isOrderingCompatible(endpoints)
        && hasEdgeConnectingInternal(endpoints.nodeU(), endpoints.nodeV());
  }

    @Override
    public SortedMap<R, Map<C, V>> headMap(R toKey) {
      checkNotNull(toKey);
      return new StandardRowSortedTable<R, C, V>(sortedBackingMap().headMap(toKey), factory)
          .rowMap();
    }

    @Override
    public SortedMap<R, Map<C, V>> subMap(R fromKey, R toKey) {
      checkNotNull(fromKey);
      checkNotNull(toKey);

  }

  @Override
  public boolean hasEdgeConnecting(N nodeU, N nodeV) {
    checkNotNull(nodeU);
    checkNotNull(nodeV);
    return nodes().contains(nodeU) && successors(nodeU).contains(nodeV);
  }

  @Override
  public boolean hasEdgeConnecting(EndpointPair<N> endpoints) {
    checkNotNull(endpoints);
    if (!isOrderingCompatible(endpoints)) {
      return false;
    }