code: def tearDown(self):
      # Set the IGNORE_PERF_VAR variable back to it's original value.
      if self._original_ignore_perf_value is not None:
          os.environ[
              self.IGNORE_PERF_VAR
          ] = self._original_ignore_perf_value
      else:
          del os.environ[self.IGNORE_PERF_VAR]
  
      mixed_precision.disable_mixed_precision_graph_rewrite_v1()
      super(MixedPrecisionTest, self).tearDown()
  
imports: import os
  from absl.testing import parameterized
  from tensorflow.core.protobuf import config_pb2
  from tensorflow.python.client import session
  from tensorflow.python.eager import context
  from tensorflow.python.eager import def_function
  from tensorflow.python.framework import config
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import variables
  from tensorflow.python.platform import test
  from tensorflow.python.platform import tf_logging
  from tensorflow.python.training import gradient_descent
  from tensorflow.python.training.experimental import loss_scale_optimizer
  from tensorflow.python.training.experimental import mixed_precision
  from tensorflow.python.training.experimental import mixed_precision_global_state
label_desc: Use image node_id 2 for calling the MixedPrecisionTest obj's underlying member method code with example usage: obj.tearDown() without return types