auto v = MatMul(scope, t, u);
    TF_ASSERT_OK(scope.status());
    CHECK_NOTNULL(v.node());

    auto x = Const(scope, {{5.0, 6.0}, {7.0, 8.0}});
    auto y = Const(scope, {{1.0, 0.0}, {0.0, 1.0}});
    auto z = MatMul(scope, x, y);
    TF_ASSERT_OK(scope.status());
    CHECK_NOTNULL(z.node());

    if (expected) {
      // Construct backward graph.