code: public static <T> Observable<T> map(Observable<?> fromObservable, final T toValue) {
          if (fromObservable != null) {
              return fromObservable.subscribeOn(Schedulers.io())
                      .map(new RXMapper<T>(toValue));
          } else {
              return Observable.empty();
          }
      }
docs: Shortcut for mapping the output of an arbitrary observable to one returning an instance of a specific type, using the IO scheduler.
  @param fromObservable the source observable
  @param toValue the value to emit to the observer
  @param <T> the type of the value to emit
  @return an observable emitting the specified value