code: @CheckReturnValue
      @SchedulerSupport(SchedulerSupport.NONE)
      public final Maybe<T> doOnSuccess(Consumer<? super T> onSuccess) {
          return RxJavaPlugins.onAssembly(new MaybePeek<T>(this,
                  Functions.emptyConsumer(), // onSubscribe
                  ObjectHelper.requireNonNull(onSuccess, "onSubscribe is null"),
                  Functions.emptyConsumer(), // onError
                  Functions.EMPTY_ACTION,    // onComplete
                  Functions.EMPTY_ACTION,    // (onSuccess | onError | onComplete)
                  Functions.EMPTY_ACTION     // dispose
          ));
      }
docs: Calls the shared consumer with the success value sent via onSuccess for each
  MaybeObserver that subscribes to the current Maybe.
  <p>
  <img width="640" height="358" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/doOnSuccess.m.png" alt="">
  <dl>
  <dt><b>Scheduler:</b></dt>
  <dd>{@code doOnSuccess} does not operate by default on a particular {@link Scheduler}.</dd>
  </dl>
  @param onSuccess the consumer called with the success value of onSuccess
  @return the new Maybe instance