Iterable<? extends ListenableFuture<? extends V>> futures) {
    return new FutureCombiner<>(true, ImmutableList.copyOf(futures));
  }

  /**
   * A helper to create a new {@code ListenableFuture} whose result is generated from a combination
   * of input futures.
   *
   * <p>See {@link #whenAllComplete} and {@link #whenAllSucceed} for how to instantiate this class.
   *