REGISTER_GRADIENT_OP("Relu", ReluGradHelper);

Status Relu6GradHelper(const Scope& scope, const Operation& op,
                       const std::vector<Output>& grad_inputs,
                       std::vector<Output>* grad_outputs) {
  auto dx = internal::Relu6Grad(scope, grad_inputs[0], op.input(0));
  grad_outputs->push_back(dx);
  return scope.status();
}
REGISTER_GRADIENT_OP("Relu6", Relu6GradHelper);