code: def test_do_not_warn_if_session_does_not_already_exist(
      self, mock_warn
  ):
      # Set this to False, so Sessions created in previous tests do not trigger
      # the warning.
      mixed_precision_global_state.set_non_mixed_precision_session_created(
          False
      )
  
      mixed_precision.enable_mixed_precision_graph_rewrite_v1(
          gradient_descent_v1.GradientDescentOptimizer(1.0)
      )
      with session.Session():
          # Make sure the "You already have existing Sessions" warning was not
          # issued, since the Session was only created after
          # enable_mixed_precision_graph_rewrite.
          for call_arg in mock_warn.call_args_list:
              msg = call_arg[0][0]
              self.assertNotIn(
                  "You already have existing Sessions that do not use "
                  "mixed precision",
                  msg,
              )
  
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 9 for calling the MixedPrecisionTest obj's underlying member method code with example usage: obj.test_do_not_warn_if_session_does_not_already_exist(mock_warn) without return types