code: public final <U> ParallelFlux<U> transform(Function<? super ParallelFlux<T>, ParallelFlux<U>> composer) {
  		return onAssembly(as(composer));
  	}
docs: Allows composing operators, in assembly time, on top of this {@link ParallelFlux}
  and returns another {@link ParallelFlux} with composed features.
  
  @param <U> the output value type
  @param composer the composer function from {@link ParallelFlux} (this) to another
  ParallelFlux
  
  @return the {@link ParallelFlux} returned by the function