code: def testIteratorGetNextAsOptionalOnGPU(self):
      if not test_util.is_gpu_available():
          self.skipTest("No GPU available")
  
      host_dataset = dataset_ops.Dataset.range(3)
      device_dataset = host_dataset.apply(
          prefetching_ops.copy_to_device("/gpu:0")
      )
      with ops.device("/gpu:0"):
          iterator = dataset_ops.make_initializable_iterator(
              device_dataset
          )
          next_elem = iterator_ops.get_next_as_optional(iterator)
          elem_has_value_t = next_elem.has_value()
          elem_value_t = next_elem.get_value()
  
      with self.cached_session(
          config=config_pb2.ConfigProto(allow_soft_placement=False)
      ):
          # Before initializing the iterator, evaluating the optional fails with
          # a FailedPreconditionError.
          with self.assertRaises(errors.FailedPreconditionError):
              self.evaluate(elem_has_value_t)
          with self.assertRaises(errors.FailedPreconditionError):
              self.evaluate(elem_value_t)
  
          # For each element of the dataset, assert that the optional evaluates to
          # the expected value.
          self.evaluate(iterator.initializer)
          for i in range(3):
              elem_has_value, elem_value = self.evaluate(
                  [elem_has_value_t, elem_value_t]
              )
              self.assertTrue(elem_has_value)
              self.assertEqual(i, elem_value)
  
          # After exhausting the iterator, `next_elem.has_value()` will evaluate to
          # false, and attempting to get the value will fail.
          for _ in range(2):
              self.assertFalse(self.evaluate(elem_has_value_t))
              with self.assertRaises(errors.InvalidArgumentError):
                  self.evaluate(elem_value_t)
  
imports: from absl.testing import parameterized
  from tensorflow.core.protobuf import config_pb2
  from tensorflow.python.data.experimental.ops import prefetching_ops
  from tensorflow.python.data.experimental.ops import testing
  from tensorflow.python.data.kernel_tests import test_base
  from tensorflow.python.data.ops import dataset_ops
  from tensorflow.python.data.ops import iterator_ops
  from tensorflow.python.data.ops import options
  from tensorflow.python.data.util import structure
  from tensorflow.python.framework import combinations
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import errors
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import sparse_tensor
  from tensorflow.python.framework import test_util
  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 22 for calling the CopyToDeviceTest obj's underlying member method code with example usage: obj.testIteratorGetNextAsOptionalOnGPU() without return types