// string is empty, no mutation has occurred. Otherwise the string is a
  // description of the mutation suitable for returning to the user.
  //
  // Sessions are added to this map in TF_NewSession, and removed in
  // TF_DeleteSession.
  // TF_Graph may only / must be deleted when
  //   sessions.size() == 0 && delete_requested == true
  //

  return names;
}

CSession::CSession(TF_Graph* graph, TF_Status* s, bool use_XLA) {
  TF_SessionOptions* opts = TF_NewSessionOptions();
  TF_EnableXLACompilation(opts, use_XLA);
  session_ = TF_NewSession(graph, opts, s);
  TF_DeleteSessionOptions(opts);
}

CSession::CSession(TF_Session* session) : session_(session) {}

CSession::~CSession() {
  TF_Status* s = TF_NewStatus();
  CloseAndDelete(s);

                                                             TF_DeleteGraph);

  TF_SessionOptions* opts = TF_NewSessionOptions();
  TF_Session* sess = TF_NewSession(graph.get(), opts, s);
  TF_DeleteSessionOptions(opts);

  const string gpu_device_name = GPUDeviceName(sess);
  TF_DeleteSession(sess, s);
  CHECK_EQ(TF_OK, TF_GetCode(s)) << TF_Message(s);

// kept alive for the lifetime of the returned TF_Session. New nodes can still
// be added to `graph` after this call.
TF_CAPI_EXPORT extern TF_Session* TF_NewSession(TF_Graph* graph,
                                                const TF_SessionOptions* opts,
                                                TF_Status* status);

TF_Session::TF_Session(tensorflow::Session* s, TF_Graph* g)
    : session(s), graph(g), last_num_graph_nodes(0), extend_before_run(true) {}

TF_Session* TF_NewSession(TF_Graph* graph, const TF_SessionOptions* opt,
                          TF_Status* status) {
  Session* session;
  status->status = NewSession(opt->options, &session);
  if (status->status.ok()) {