code: public static <R> Observable<R> fromAction(Action0 action, R result, Scheduler scheduler) {
          return Observable.create(OperatorFromFunctionals.fromAction(action, result)).subscribeOn(scheduler);
      }
docs: Return an Observable that calls the given action and emits the given result when an Observer subscribes.
  <p>
  <img width="640" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/fromAction.s.png" alt="">
  
  @param <R> the return type
  @param action the action to invoke on each subscription
  @param scheduler the Scheduler where the function is called and the result is emitted
  @param result the result to emit to observers
  @return an Observable that calls the given action and emits the given result when an Observer subscribes
  @see <a href="https://github.com/ReactiveX/RxJava/wiki/Async-Operators#wiki-fromaction">RxJava Wiki: fromAction()</a>