code: def tearDown(self):
      super(TPUEstimatorTest, self).tearDown()
      del os.environ["TF_CONFIG"]
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import itertools
  import json
  import os
  from absl.testing import parameterized
  from adanet import tf_compat
  from adanet.core import testing_utils
  from adanet.core.tpu_estimator import TPUEstimator
  from adanet.subnetwork import Builder
  from adanet.subnetwork import Report
  from adanet.subnetwork import SimpleGenerator
  from adanet.subnetwork import Subnetwork
  import numpy
  import tensorflow.compat.v2
  from tensorflow_estimator.python.estimator.head import regression_head
label_desc: Use image node_id 2 for calling the TPUEstimatorTest obj's underlying member method code with example usage: obj.tearDown() without return types