def basic_bn_shortcut(model, prefix, blob_in, dim_in, dim_out, stride):
    """ For a pre-trained network that used BN. An AffineChannel op replaces BN
    during fine-tuning.
    """

    if dim_in == dim_out:
        return blob_in

    c = model.Conv(
        blob_in,
        prefix + '_branch1',
        dim_in,
        dim_out,
        kernel=1,
        stride=stride,
        no_bias=1
    )
    return model.AffineChannel(c, prefix + '_branch1_bn', dim=dim_out)
 For a pre-trained network that used BN. An AffineChannel op replaces BN
    during fine-tuning.
    
detectron/modeling/ResNet.py