message: Add a note that stop_gradient in moments does not change the gradient
diff: @@ -689,6 +689,9 @@ def moments(
  # Compute true mean while keeping the dims for proper broadcasting.
  mean = math_ops.reduce_mean(y, axes, keepdims=True, name="mean")
  # sample variance, not unbiased variance
  + # Note: stop_gradient does not change the gradient that gets
  + # backpropagated to the mean from the variance calculation,
  + # because that gradient is zero
  variance = math_ops.reduce_mean(
  math_ops.squared_difference(y, array_ops.stop_gradient(mean)),
  axes,
  