message: Add test when axis is an empty list
diff: @@ -123,6 +123,8 @@ class UniqueTest(test.TestCase):
  self.assertEqual(idx.shape.as_list(), [2])
  _, idx = gen_array_ops.unique_v2(x, axis=[-3])
  self.assertEqual(idx.shape.as_list(), [3])
  + _, idx = gen_array_ops.unique_v2([0, 1, 2], axis=[])
  + self.assertEqual(idx.shape.as_list(), [3])
  with self.assertRaisesRegexp(ValueError, "axis expects a 1D vector"):
  gen_array_ops.unique_v2(x, axis=[[0]])
  