code: public final Mono<T> or(Mono<? extends T> other) {
  		if (this instanceof MonoFirst) {
  			MonoFirst<T> a = (MonoFirst<T>) this;
  			Mono<T> result =  a.orAdditionalSource(other);
  			if (result != null) {
  				return result;
  			}
  		}
  		return first(this, other);
  	}
docs: Emit the first available result from this mono or the other mono.
  
  <p>
  <img class="marble" src="doc-files/marbles/orForMono.svg" alt="">
  
  @param other the racing other {@link Mono} to compete with for the result
  
  @return a new {@link Mono}
  @see #first