How to change all BN layers to GN

Hi

when I use your method I get the following error:

Traceback (most recent call last):
  File "train_discriminator.py", line 170, in <module>
    norm_layer=MyGroupNorm)
  File "/alto/nima/torch-env/lib/python3.6/site-packages/torchvision/models/resnet.py", line 192, in __init__
    nn.init.constant_(m.weight, 1)
  File "/alto/nima/torch-env/lib/python3.6/site-packages/torch/nn/init.py", line 176, in constant_
    return _no_grad_fill_(tensor, val)
  File "/alto/nima/torch-env/lib/python3.6/site-packages/torch/nn/init.py", line 59, in _no_grad_fill_
    return tensor.fill_(val)
AttributeError: 'NoneType' object has no attribute 'fill_'