// Initialize theta[i] - epsilon.
    memcpy(&thetaMinus_data[0], TF_TensorData(theta_tensor),
           TF_TensorByteSize(theta_tensor));
    thetaMinus_data[i] -= epsilon;
    AbstractTensorHandlePtr thetaMinus;
    {
      AbstractTensorHandle* thetaMinus_raw = nullptr;
      TF_RETURN_IF_ERROR(TestTensorHandleWithDims<float, TF_FLOAT>(
          ctx, thetaMinus_data.data(), theta_dims.data(), num_dims,