Method biFlatMap

future-java/src/main/java/io/trane/future/NoFuture.java:50–55

(final Future<U> other,
      final BiFunction<? super T, ? super U, ? extends Future<R>> f)

  }

  @SuppressWarnings("unchecked")
  @Override
  public <U, R> Future<R> biFlatMap(final Future<U> other,
      final BiFunction<? super T, ? super U, ? extends Future<R>> f) {
    return (Future<R>) this;
  }

  @Override
  public Future<T> ensure(final Runnable r) {