class_docstr: Tests for timeline
code: def tearDownClass(cls):
      # file_name is just a temprary file generated in bluefog timeline
      file_name = f"{cls.temp_file}{bf.rank()}.json"
      os.remove(file_name)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import os
  import time
  import threading
  import unittest
  import warnings
  import torch
  import bluefog.torch
  from bluefog.common import topology_util
  from bluefog.common.util import env
label_desc: Use image node_id 3 for calling the TimelineTests obj's underlying member method code with example usage: obj.tearDownClass(cls) without return types