Status PowGrad(const Scope& scope, const Operation& op,
               const std::vector<Output>& grad_inputs,
               std::vector<Output>* grad_outputs) {
  auto x = ConjugateHelper(scope, op.input(0));
  auto y = ConjugateHelper(scope, op.input(1));
  auto z = ConjugateHelper(scope, op.output(0));
  auto grad = grad_inputs[0];
  // grad * y * pow(x, y - 1)
  auto one = Cast(scope, Const(scope, 1.0), y.type());
  auto gx_1 =