TF_Operation* add2 = Add(add1, feed3, func_graph_, s_, "add2");
  Define(-1, {}, {feed1, feed2, feed3}, {add1, add2}, {"my_out", "my_out"},
         true);
  EXPECT_EQ(TF_INVALID_ARGUMENT, TF_GetCode(s_));
  EXPECT_EQ(string("Cannot have duplicate output names. Name 'my_out' "
                   "appears more than once in 'output_names' array."),
            string(TF_Message(s_)));
}

  EXPECT_TF_META("v", -1, TF_ATTR_TENSOR, -1);
  TF_Tensor* t_out = nullptr;
  TF_OperationGetAttrTensor(oper, "v", &t_out, s_);
  ASSERT_EQ(TF_OK, TF_GetCode(s_)) << TF_Message(s_);
  EXPECT_EQ(TF_STRING, TF_TensorType(t_out));
  EXPECT_EQ(0, TF_NumDims(t_out));
  ASSERT_EQ(TF_TensorByteSize(t_in.get()), TF_TensorByteSize(t_out));
  TF_TString* t_in_tstr = static_cast<TF_TString*>(TF_TensorData(t_in.get()));