Thanks for your help 
However my objective is to change gammas and betas even when they are not learnable (affine=False).
By deafault affine=False means that gammas are set to 1s, and are not parameters. I want to change this to some other value than 1 and still have BN gammas not learnable.
The best would be to rewrite my own BN module but I can’t figure out where the gammas are set to 1 in the case of afffine=False since they are set to None.
Thanks!