/// \brief A handle to a subgraph, created with
  /// `ClientSession::MakeCallable()`.
  typedef int64_t CallableHandle;

  /// \brief Creates a `handle` for invoking the subgraph defined by
  /// `callable_options`.
  /// NOTE: This API is still experimental and may change.
  Status MakeCallable(const CallableOptions& callable_options,
                      CallableHandle* out_handle);

using tensorflow::StructuredValue;
using tensorflow::TensorSpecProto;
using tensorflow::libexport::TFPackage;
using tensorflow::protobuf::RepeatedPtrField;
using tensorflow::tracing::graph::GraphFunction;

TaggedValue MakeCallable(const std::string& fn_name, Function fn,
                         AbstractContext* ctx) {
  auto CallFn = [fn_name, fn, ctx](TaggedValue args_,
                                   TaggedValue kwargs_) -> TaggedValue {

                               threadpool_options);
}

Status ClientSession::MakeCallable(const CallableOptions& callable_options,
                                   CallableHandle* out_handle) {
  TF_RETURN_IF_ERROR(impl()->MaybeExtendGraph());
  return impl()->session_->MakeCallable(callable_options, out_handle);
}

Status ClientSession::RunCallable(CallableHandle handle,

  CallableOptions options;
  options.add_feed(a.node()->name());
  options.add_feed(b.node()->name());
  options.add_fetch(c.node()->name());
  ClientSession::CallableHandle callable;
  TF_CHECK_OK(session.MakeCallable(options, &callable));
  TF_EXPECT_OK(session.RunCallable(
      callable, {test::AsTensor<int>({1}, {}), test::AsTensor<int>({41}, {})},
      &outputs, nullptr));

    return wrapped_->ListDevices(response);
  }

  Status Close() override { return wrapped_->Close(); }

  Status MakeCallable(const CallableOptions& callable_options,
                      CallableHandle* out_handle) override {
    return wrapped_->MakeCallable(callable_options, out_handle);
  }

  Status RunCallable(CallableHandle handle,
                     const std::vector<Tensor>& feed_tensors,