code: public static <T> Observable.Transformer<T, T> applyCustomSchedulers(final Handler subscribeHandler) {
          return new Observable.Transformer<T, T>() {
              @Override
              public Observable<T> call(Observable<T> observable) {
                  return observable.subscribeOn(HandlerScheduler.from(subscribeHandler))
                          .observeOn(AndroidSchedulers.mainThread());
              }
          };
      }
docs: <p>
  Apply the subscribeOn/observeOn transformation of {custom_handler}/mainThread
  to an observable via compose()
  </p>
  
  <p>
  Only apply this to observables that are handling computation tasks in the background. Basically
  all non-IO work
  </p>
  
  @param <T>       the transformation type
  @return          the observable post-transform