message: [tf.data] Adds more coverage for Defun-defun switch, adds map unit test.
diff: @@ -705,6 +705,13 @@ class MapTest(test_base.DatasetTestBase, parameterized.TestCase):
  with self.assertRaises(errors.OutOfRangeError):
  self.evaluate(get_next())
  + def testNestedListMapDataset(self):
  + dataset = dataset_ops.Dataset.from_tensors(
  + [0, 1, 2]).repeat(10).map(lambda a: ([a[1], a[0] + a[2]], a[1]))
  +
  + expected_output = [(np.array([1, 2]), 1)] * 10
  + self.assertDatasetProduces(dataset, expected_output=expected_output)
  +
  def testPrefetch(self):
  # We will use this event to test that `_map_py_func()` has been
  # invoked a certain number of times (6 times, to be exact) after
  