code: def testV1CompatibilityDummyInvisibleDeviceList(self):
      gpus = config.list_physical_devices("GPU")
      if gpus:
          self.skipTest("Test requires no GPUs")
  
      # Ensure GPU options left untouched on CPU only environments
      context.context()._physical_devices = None
      context.context()._config = config_pb2.ConfigProto(
          gpu_options=config_pb2.GPUOptions(visible_device_list="0")
      )
      new_config = context.context().config
      self.assertEqual(new_config.gpu_options.visible_device_list, "0")
  
imports: from absl.testing import parameterized
  from tensorflow.core.protobuf import cluster_pb2
  from tensorflow.core.protobuf import config_pb2
  from tensorflow.core.protobuf import rewriter_config_pb2
  from tensorflow.core.protobuf import tensorflow_server_pb2
  from tensorflow.python.eager import context
  from tensorflow.python.eager import def_function
  from tensorflow.python.framework import config
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import errors
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import test_ops
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import math_ops
  from tensorflow.python.platform import test
  from tensorflow.python.util import compat
label_desc: Use image node_id 21 for calling the DeviceTest obj's underlying member method code with example usage: obj.testV1CompatibilityDummyInvisibleDeviceList() without return types