public final <R> ParallelFlux<R> flatMap(Function<? super T, ? extends Publisher<? extends R>> mapper,
			boolean delayError,
			int maxConcurrency) {
		return flatMap(mapper,
				delayError,
				maxConcurrency, Queues.SMALL_BUFFER_SIZE);
	}
public final <R> ParallelFlux<R> flatMap(Function<? super T, ? extends Publisher<? extends R>> mapper,
			boolean delayError,
			int maxConcurrency) {
		return flatMap(mapper,
				delayError,
				maxConcurrency, Queues.SMALL_BUFFER_SIZE);
	}
public final < R > ParallelFlux < R > flatMap ( Function < ? super T , ? extends Publisher < ? extends R > > mapper , boolean delayError , int maxConcurrency ) { return flatMap ( mapper , delayError , maxConcurrency , Queues . SMALL_BUFFER_SIZE ) ; }
Generates and flattens Publishers on each 'rail', optionally delaying errors and
having a total number of simultaneous subscriptions to the inner Publishers.
<p>
It uses a default inner prefetch.

@param <R> the result type
@param mapper the function to map each rail's value into a Publisher
@param delayError should the errors from the main and the inner sources delayed
till everybody terminates?
@param maxConcurrency the maximum number of simultaneous subscriptions to the
generated inner Publishers

@return the new {@link ParallelFlux} instance
Generates and flattens Publishers on each rail optionally delaying errors and having a total number of simultaneous subscriptions to the inner Publishers . <p > It uses a default inner prefetch .