code: public List<SubtaskInformation> listSubtasks(String jobId, String taskId) throws BatchErrorException, IOException {
          return listSubtasks(jobId, taskId, null, null);
      }
docs: Lists the {@link SubtaskInformation subtasks} of the specified task.
  
  @param jobId
  The ID of the job containing the task.
  @param taskId
  The ID of the task.
  @return A list of {@link SubtaskInformation} objects.
  @throws BatchErrorException
  Exception thrown when an error response is received from the
  Batch service.
  @throws IOException
  Exception thrown when there is an error in
  serialization/deserialization of data sent to/received from the
  Batch service.