code: public final <R> Flux<R> flatMapIterable(Function<? super T, ? extends Iterable<? extends R>> mapper) {
  		return Flux.onAssembly(new MonoFlattenIterable<>(this, mapper, Integer
  				.MAX_VALUE, Queues.one()));
  	}
docs: Transform the item emitted by this {@link Mono} into {@link Iterable}, then forward
  its elements into the returned {@link Flux}. The prefetch argument allows to
  give an arbitrary prefetch size to the inner {@link Iterable}.
  
  <p>
  <img class="marble" src="doc-files/marbles/flatMapIterableForMono.svg" alt="">
  
  @param mapper the {@link Function} to transform input item into a sequence {@link Iterable}
  @param <R> the merged output sequence type
  
  @return a merged {@link Flux}