code: public final Flux<T> startWith(Publisher<? extends T> publisher) {
  		if (this instanceof FluxConcatArray) {
  			FluxConcatArray<T> fluxConcatArray = (FluxConcatArray<T>) this;
  			return fluxConcatArray.concatAdditionalSourceFirst(publisher);
  		}
  		return concat(publisher, this);
  	}
docs: Prepend the given {@link Publisher} sequence to this {@link Flux} sequence.
  
  <p>
  <img class="marble" src="doc-files/marbles/startWithPublisher.svg" alt="">
  
  @param publisher the Publisher whose values to prepend
  
  @return a new {@link Flux} prefixed with the given {@link Publisher} sequence