auto y = ConjugateHelper(grad_scope, op.output(0));
  grad_outputs->push_back(internal::TanhGrad(grad_scope, y, grad));
  return grad_scope.status();
}
REGISTER_GRADIENT_OP("Tanh", TanhGrad);

Status AsinhGrad(const Scope& scope, const Operation& op,
                 const std::vector<Output>& grad_inputs,
                 std::vector<Output>* grad_outputs) {
  // y = asinh(x)
  // dy/dx = 1 / cosh(y)