code: public void cancelAndRemove(Observer<?> observer, String observableTag) {
      cancelAndRemove(Utils.getObserverTag(observer), observableTag);
    }
docs: Removes the {@link Observable} identified by {@code observableTag} for the given
  {@link Observer} and cancels it subscription.
  No more events will be delivered to its subscriber.
  <p>If no Observable is found for the provided {@code observableTag}, nothing happens.