code: public final <V> Flux<V> switchMap(Function<? super T, Publisher<? extends V>> fn, int prefetch) {
  		return onAssembly(new FluxSwitchMap<>(this, fn, Queues.unbounded(prefetch), prefetch));
  	}
docs: Switch to a new {@link Publisher} generated via a {@link Function} whenever
  this {@link Flux} produces an item. As such, the elements from each generated
  Publisher are emitted in the resulting {@link Flux}.
  
  <p>
  <img class="marble" src="doc-files/marbles/switchMap.svg" alt="">
  
  @param fn the {@link Function} to generate a {@link Publisher} for each source value
  @param prefetch the produced demand for inner sources
  
  @param <V> the type of the return value of the transformation function
  
  @return a new {@link Flux} that emits values from an alternative {@link Publisher}
  for each source onNext