code: public synchronized LottieTask<T> addFailureListener(LottieListener<Throwable> listener) {
      if (result != null && result.getException() != null) {
        listener.onResult(result.getException());
      }
  
      failureListeners.add(listener);
      return this;
    }
docs: Add a task failure listener. This will only be called in the even that an exception
  occurs. If an exception has already occurred, the listener will be called immediately.
  @return the task for call chaining.