def METHOD_NAME(self, folder_id, sender):
    if not folder_id:
        return []
    task_cache = self._tasks_cache.get(folder_id)
    if task_cache is None or not task_cache.is_valid:
        self._refresh_tasks_cache(folder_id, sender)
        task_cache = self._tasks_cache.get(folder_id)
    return task_cache.get_data()