code: @NonNull
      private static ObservableTransformer<Boolean, Boolean> onSubscribeSetText(Button button, @StringRes int textResId) {
          return booleanObservable -> booleanObservable
                  .doOnSubscribe((disposable) -> button.setText(textResId))
                  .subscribeOn(AndroidSchedulers.mainThread());
      }
docs: Function that returns a {@link io.reactivex.ObservableTransformer} which will on subscribe
  set a text on a button using a proper thread
  
  @param button the button to set text on
  @param textResId the text resource id
  @return the transformer