code: def get_task_fs(self, courseid, taskid):
          
          if not id_checker(courseid):
              raise InvalidNameException("Course with invalid name: " + courseid)
          if not id_checker(taskid):
              raise InvalidNameException("Task with invalid name: " + taskid)
          return self._filesystem.from_subfolder(courseid).from_subfolder(taskid)
docs: :param courseid: the course id of the course
          :param taskid: the task id of the task
          :raise InvalidNameException
          :return: A FileSystemProvider to the folder containing the task files