code: public static <T> Publisher<T> toPublisher(Observable<T> observable) {
          return new PublisherAdapter<T>(observable);
      }
docs: Convert a Rx {@link Observable} into a Reactive Streams {@link Publisher}.
  <p/>
  Use this method when you have an RxJava observable, that you want to be consumed by another library.
  
  @param <T> the value type
  @param observable the {@link Observable} to convert
  @return the converted {@link Publisher}