name_ = std::move(name);
  }

  void set_op(string op) {
    DCHECK(IsEmpty());
    op_ = std::move(op);
  }

  void set_assigned_device(string assigned_device) {
    DCHECK(IsEmpty());
    assigned_device_ = std::move(assigned_device);
  }

  void set_constant_value(Tensor constant_value) {
    DCHECK(IsEmpty());
    constant_value_ = std::move(constant_value);
    op_ = "Const";
  }

  Impl(const Scope& other, Tags::Colocate, const Operation& colocate_with_op,
       bool clear_colocations);
  Impl(const Scope& other, Tags::AssignedDevice, const string& assigned_device);
  Impl(const Scope& other, Tags::XlaCluster, const string& xla_cluster);

  std::unordered_set<string> GetColocationConstraints(
      const Operation& colocate_with_op) const;

      assigned_add.node(),
      NodeWith(AssignedDevice("/job:localhost/replica:0/task:0/device:CPU:0")));
  EXPECT_THAT(unassigned_add.node(), NodeWith(AssignedDevice("")));

  EXPECT_EQ(Explain(unassigned_add.node(),
                    NodeWith(AssignedDevice(
                        "/job:localhost/replica:0/task:0/device:CPU:0"))),
            "\nexpected assigned_device "