code: public static  Mono<Void> whenDelayError(Publisher<?>... sources) {
  		if (sources.length == 0) {
  			return empty();
  		}
  		if (sources.length == 1) {
  			return empty(sources[0]);
  		}
  		return onAssembly(new MonoWhen(true, sources));
  	}
docs: Merge given publishers into a new {@literal Mono} that will be fulfilled when
  all of the given {@literal sources} have completed. Errors from the sources are delayed.
  If several Publishers error, the exceptions are combined (as suppressed exceptions on a root exception).
  
  <p>
  <img class="marble" src="doc-files/marbles/whenDelayError.svg" alt="">
  <p>
  @param sources The sources to use.
  
  @return a {@link Mono}.