code: public static <T> Flux<T> mergeSequentialDelayError(Publisher<? extends Publisher<? extends T>> sources,
  			int maxConcurrency, int prefetch) {
  		return mergeSequential(sources, true, maxConcurrency, prefetch);
  	}
docs: Merge data from {@link Publisher} sequences emitted by the passed {@link Publisher}
  into an ordered merged sequence. Unlike concat, the inner publishers are subscribed to
  eagerly (but at most {@code maxConcurrency} sources at a time). Unlike merge, their
  emitted values are merged into the final sequence in subscription order.
  This variant will delay any error until after the rest of the mergeSequential backlog has been processed.
  <p>
  <img class="marble" src="doc-files/marbles/mergeSequentialAsyncSources.svg" alt="">
  
  @param sources a {@link Publisher} of {@link Publisher} sources to merge
  @param prefetch the inner source request size
  @param maxConcurrency the request produced to the main source thus limiting concurrent merge backlog
  @param <T> the merged type
  
  @return a merged {@link Flux}, subscribing early but keeping the original ordering