code: @CheckReturnValue
      @BackpressureSupport(BackpressureKind.FULL)
      @SchedulerSupport(SchedulerSupport.COMPUTATION)
      public final Flowable<T> timeout(long timeout, TimeUnit timeUnit, Publisher<? extends T> other) {
          ObjectHelper.requireNonNull(other, "other is null");
          return timeout0(timeout, timeUnit, other, Schedulers.computation());
      }
docs: Returns a Flowable that mirrors the source Publisher but applies a timeout policy for each emitted
  item. If the next item isn't emitted within the specified timeout duration starting from its predecessor,
  the resulting Publisher begins instead to mirror a fallback Publisher.
  <p>
  <img width="640" height="305" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/timeout.2.png" alt="">
  <dl>
  <dt><b>Backpressure:</b></dt>
  <dd>The operator honors backpressure from downstream. The {@code Publisher}
  sources are expected to honor backpressure as well.
  If any of the source {@code Publisher}s violate this, it <em>may</em> throw an
  {@code IllegalStateException} when the source {@code Publisher} completes.</dd>
  <dt><b>Scheduler:</b></dt>
  <dd>This version of {@code timeout} operates by default on the {@code computation} {@link Scheduler}.</dd>
  </dl>
  
  @param timeout
  maximum duration between items before a timeout occurs
  @param timeUnit
  the unit of time that applies to the {@code timeout} argument
  @param other
  the fallback Publisher to use in case of a timeout
  @return the source Publisher modified to switch to the fallback Publisher in case of a timeout
  @see <a href="http://reactivex.io/documentation/operators/timeout.html">ReactiveX operators documentation: Timeout</a>