code: public final Mono<Void> thenEmpty(Publisher<Void> other) {
  		return then(Mono.fromDirect(other));
  	}
docs: Return a {@code Mono<Void>} that waits for this {@link Flux} to complete then
  for a supplied {@link Publisher Publisher&lt;Void&gt;} to also complete. The
  second completion signal is replayed, or any error signal that occurs instead.
  <p>
  <img class="marble" src="doc-files/marbles/thenEmptyForFlux.svg" alt="">
  
  @reactor.discard This operator discards elements from the source.
  
  @param other a {@link Publisher} to wait for after this Flux's termination
  @return a new {@link Mono} completing when both publishers have completed in
  sequence