Swin backbone missing requirements

[urimerhav]

def build_vm(args):
    device = torch.device(args.device)

    if 'swin' in args.backbone:
        from .swin_transformer import build_swin_backbone
        backbone = build_swin_backbone(args)
    else:
        backbone = build_backbone(args)

swin_transformer isn't a defined requirements. I've scoured the official swin repo and it doesn't seem to have a function called build_swin_backbone. The only instance of this function name I could fine is this:

https://github.com/megvii-research/SOLQ

Is that the right dependency? If so, maybe added this to the docs and in a comment above this import?