constexpr char kQueueName[] = "unit_test";
constexpr char kQueueName0[] = "q0";
constexpr char kQueueName1[] = "q1";
constexpr char kSquareOpName[] = "square";
constexpr char kVarOpName[] = "var";

GraphDef BuildSimpleGraph() {
  Scope root = Scope::NewRootScope();
  auto init_value = Const(root, 0);
  auto var = Variable(root.WithOpName(kVarOpName), TensorShape({}),
                      DataType::DT_INT32);