We have customized a complex activation function, such as
y = relu(0, x / sigma)

The x is the  output of a  conv layer and the sigma‘s  value is  related to the weight  of the conv layer
in backward process,we need to update the weight of the conv layer.Theoretically，we should calculate the Partial derivative of x and sigma.Is the pytorch can do it automatically？
Should we define the  derivative formula？If we should do it，where I should define?