code: def setUp(self):
      super().setUp()
      test_utils.ensure_flag("test_tmpdir")
  
imports: import functools
  import io
  from unittest import mock
  from absl.testing import absltest
  from absl.testing import parameterized
  import gym
  import numpy
  from trax import models
  from trax import test_utils
  from trax.data import inputs
  from trax.layers import test_utils
  from trax.rl import serialization_utils
  from trax.rl import space_serializer
  from trax.supervised import callbacks
  from trax.supervised import lr_schedules
  from trax.supervised import trainer_lib
  from trax.supervised import training
label_desc: Use image node_id 1 for calling the CallbacksTest obj's underlying member method code with example usage: obj.setUp() without return types