// Initialize theta[i] + epsilon.
    memcpy(thetaPlus_data.data(), TF_TensorData(theta_tensor),
           TF_TensorByteSize(theta_tensor));
    thetaPlus_data[i] += epsilon;
    AbstractTensorHandlePtr thetaPlus;
    {
      AbstractTensorHandle* thetaPlus_raw = nullptr;
      TF_RETURN_IF_ERROR(TestTensorHandleWithDims<float, TF_FLOAT>(
          ctx, thetaPlus_data.data(), theta_dims.data(), num_dims,