class FlowableFlatMap extends AbstractFlowableWithUpstream<T, U> {

    public static <T, U> FlowableSubscriber<T> subscribe(Subscriber<? super U> s,
            Function<? super T, ? extends Publisher<? extends U>> mapper,
            boolean delayErrors, int maxConcurrency, int bufferSize) {
        return new MergeSubscriber<T, U>(s, mapper, delayErrors, maxConcurrency, bufferSize);
    }

    public  FlowableFlatMap(Flowable<T> source,
            Function<? super T, ? extends Publisher<? extends U>> mapper,
            boolean delayErrors, int maxConcurrency, int bufferSize);

}