reactor-core/src/main/java/reactor/core/publisher/ParallelFlux.java
public final <U> ParallelFlux<U> transform(Function<? super ParallelFlux<T>, ParallelFlux<U>> composer) {
		return onAssembly(as(composer));
	}
public final <U> ParallelFlux<U> transform(Function<? super ParallelFlux<T>, ParallelFlux<U>> composer) {
		return onAssembly(as(composer));
	}
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