message: use get_item_tensor_string for string with rank 0
diff: @@ -53,6 +53,12 @@ class SlicesTest(test.TestCase):
  with self.test_session() as sess:
  self.assertEqual(sess.run(t), b"b")
  + initial_list_str = constant_op.constant(["abcd", "bcde"])
  + t = slices.get_item(initial_list_str, 1, slices.GetItemOpts(element_dtype=initial_str.dtype))
  +
  + with self.test_session() as sess:
  + self.assertEqual(sess.run(t), b"bcde")
  +
  if __name__ == '__main__':
  test.main()
  