code: public final ParallelFlux<T> doOnError(Consumer<? super Throwable> onError) {
  		Objects.requireNonNull(onError, "onError");
  		return doOnSignal(this, null, null, onError, null, null, null, null, null);
  	}
docs: Call the specified consumer with the exception passing through any 'rail'.
  
  @param onError the callback
  
  @return the new {@link ParallelFlux} instance