code: @BackpressureSupport(BackpressureKind.UNBOUNDED_IN)
      @CheckReturnValue
      @SchedulerSupport(SchedulerSupport.NONE)
      public final <U> Maybe<T> takeUntil(Publisher<U> other) {
          ObjectHelper.requireNonNull(other, "other is null");
          return RxJavaPlugins.onAssembly(new MaybeTakeUntilPublisher<T, U>(this, other));
      }
docs: Returns a Maybe that emits the item emitted by the source Maybe until a second Publisher
  emits an item.
  <p>
  <img width="640" height="380" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/takeUntil.png" alt="">
  <dl>
  <dt><b>Backpressure:</b></dt>
  <dd>The {@code Publisher} is consumed in an unbounded fashion and is cancelled after the first item
  emitted.</dd>
  <dt><b>Scheduler:</b></dt>
  <dd>{@code takeUntil} does not operate by default on a particular {@link Scheduler}.</dd>
  </dl>
  
  @param other
  the Publisher whose first emitted item will cause {@code takeUntil} to stop emitting items
  from the source Publisher
  @param <U>
  the type of items emitted by {@code other}
  @return a Maybe that emits the items emitted by the source Maybe until such time as {@code other} emits its first item
  @see <a href="http://reactivex.io/documentation/operators/takeuntil.html">ReactiveX operators documentation: TakeUntil</a>