Output SafeDivHelper(const Scope& scope, const Output& x, const Output& y) {
  return Div(scope, x, Maximum(scope, y, Const(scope, 1)));
}

// SumGradHelper returns the gradient for the Sum operator, and is used
// by SumGrad and MeanGrad.
Output SumGradHelper(const Scope& scope, const Operation& op,
                     const std::vector<Output>& grad_inputs) {
  // The partial derivative for any input along a "reduced" dimension