@CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.CUSTOM)
    public final Completable delay(final long delay, final TimeUnit unit, final Scheduler scheduler, final boolean delayError) {
        ObjectHelper.requireNonNull(unit, "unit is null");
        ObjectHelper.requireNonNull(scheduler, "scheduler is null");
        return RxJavaPlugins.onAssembly(new CompletableDelay(this, delay, unit, scheduler, delayError));
    }