core::RefCountPtr<AbstractFunction> scoped_func;
    // Returning null tensors from a tf.function is not supported, so we keep
    // track of indices in the model's outputs are nullptr in this set.
    // The FunctionDef only outputs the non-null tensors. We later pad the
    // function op outputs to have nullptrs at the `null_indices`.
    absl::flat_hash_set<int> null_indices;
    {
      AbstractContextPtr func_ctx(BuildFunction(fn_name));

  const string malformed_text_proto(R"(cluster {
  job {
    name: "worker")");
  TF_Buffer* null_result =
      TFE_GetServerDef(malformed_text_proto.c_str(), status);
  EXPECT_NE(TF_GetCode(status), TF_OK);
  EXPECT_TRUE(absl::StrContains(TF_Message(status),
                                "Invalid text proto for ServerDef"));
  EXPECT_EQ(null_result, nullptr);

  // Cleanup
  TF_DeleteBuffer(result);
  TF_DeleteStatus(status);
}

  DefineFunction("MyGrad1", &grad_func1);
  DefineFunction("MyGrad2", &grad_func2);

  // func cannot be null
  TF_GraphCopyFunction(host_graph_, nullptr, func_, s_);
  EXPECT_EQ(TF_INVALID_ARGUMENT, TF_GetCode(s_));
  EXPECT_EQ(string("'func' argument to TF_GraphCopyFunction cannot be null"),
            string(TF_Message(s_)));

  // Cannot change gradient

    status->status =
        tensorflow::errors::InvalidArgument("Unparseable AttrValue proto");
    return;
  }
  if (op == nullptr) {
    status->status = tensorflow::errors::InvalidArgument(
        "Got a null or uninitialized `op` argument");
    return;
  }
  tensorflow::EagerOperation* operation =
      OperationFromInterface(tensorflow::unwrap(const_cast<TFE_Op*>(op)));