code: public static <T> ParallelFlux<T> from(Publisher<? extends T> source,
  			int parallelism,
  			int prefetch,
  			Supplier<Queue<T>> queueSupplier) {
  		Objects.requireNonNull(queueSupplier, "queueSupplier");
  		Objects.requireNonNull(source, "source");
  
  		return onAssembly(new ParallelSource<>(source,
  				parallelism,
  				prefetch, queueSupplier));
  	}
docs: Take a Publisher and prepare to consume it on {@code parallelism} number of 'rails'
  and in a round-robin fashion and use custom prefetch amount and queue
  for dealing with the source Publisher's values.
  
  @param <T> the value type
  @param source the source Publisher
  @param parallelism the number of parallel rails
  @param prefetch the number of values to prefetch from the source
  @param queueSupplier the queue structure supplier to hold the prefetched values
  from the source until there is a rail ready to process it.
  
  @return the new {@link ParallelFlux} instance