@CheckReturnValue
    @BackpressureSupport(BackpressureKind.ERROR)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final <U, V> Flowable<Flowable<T>> window(
            Publisher<U> openingIndicator,
            Function<? super U, ? extends Publisher<V>> closingIndicator) {
        return window(openingIndicator, closingIndicator, bufferSize());
    }