code: def testNestedAddN(self):
      devices = ["/cpu:0"]
      if test_util.is_gpu_available():
          devices.append("/gpu:0")
      for device in devices:
          with ops.device(device):
              opt1 = optional_ops.Optional.from_value([1, 2.0])
              opt2 = optional_ops.Optional.from_value([3, 4.0])
              opt3 = optional_ops.Optional.from_value(
                  (5.0, opt1._variant_tensor)
              )
              opt4 = optional_ops.Optional.from_value(
                  (6.0, opt2._variant_tensor)
              )
  
              add_tensor = math_ops.add_n(
                  [opt3._variant_tensor, opt4._variant_tensor]
              )
              add_opt = optional_ops._OptionalImpl(
                  add_tensor, opt3.element_spec
              )
              self.assertEqual(
                  self.evaluate(add_opt.get_value()[0]), 11.0
              )
  
              inner_add_opt = optional_ops._OptionalImpl(
                  add_opt.get_value()[1], opt1.element_spec
              )
              self.assertAllEqual(inner_add_opt.get_value(), [4, 6.0])
  
imports: import functools
  from absl.testing import parameterized
  import numpy
  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 optional_ops
  from tensorflow.python.data.util import structure
  from tensorflow.python.eager import context
  from tensorflow.python.eager import def_function
  from tensorflow.python.framework import combinations
  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 sparse_tensor
  from tensorflow.python.framework import tensor_shape
  from tensorflow.python.framework import tensor_spec
  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
label_desc: Use image node_id 6 for calling the OptionalTest obj's underlying member method code with example usage: obj.testNestedAddN() without return types