code: @CheckReturnValue
      @BackpressureSupport(BackpressureKind.FULL)
      @SchedulerSupport(SchedulerSupport.NONE)
      public static <T> Flowable<T> fromFuture(Future<? extends T> future) {
          ObjectHelper.requireNonNull(future, "future is null");
          return RxJavaPlugins.onAssembly(new FlowableFromFuture<T>(future, 0L, null));
      }
docs: Converts a {@link Future} into a Publisher.
  <p>
  <img width="640" height="315" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/from.Future.png" alt="">
  <p>
  You can convert any object that supports the {@link Future} interface into a Publisher that emits the
  return value of the {@link Future#get} method of that object by passing the object into the {@code from}
  method.
  <p>
  <em>Important note:</em> This Publisher is blocking on the thread it gets subscribed on; you cannot cancel it.
  <p>
  Unlike 1.x, canceling the Flowable won't cancel the future. If necessary, one can use composition to achieve the
  cancellation effect: {@code futurePublisher.doOnCancel(() -> future.cancel(true));}.
  <dl>
  <dt><b>Backpressure:</b></dt>
  <dd>The operator honors backpressure from downstream.</dd>
  <dt><b>Scheduler:</b></dt>
  <dd>{@code fromFuture} does not operate by default on a particular {@link Scheduler}.</dd>
  </dl>
  
  @param future
  the source {@link Future}
  @param <T>
  the type of object that the {@link Future} returns, and also the type of item to be emitted by
  the resulting Publisher
  @return a Flowable that emits the item from the source {@link Future}
  @see <a href="http://reactivex.io/documentation/operators/from.html">ReactiveX operators documentation: From</a>