@CheckReturnValue
    @NonNull
    public final ParallelFlowable<T> runOn(@NonNull Scheduler scheduler, int prefetch) {
        ObjectHelper.requireNonNull(scheduler, "scheduler");
        ObjectHelper.verifyPositive(prefetch, "prefetch");
        return RxJavaPlugins.onAssembly(new ParallelRunOn<T>(this, scheduler, prefetch));
    }