Based on the error messages it seems that feats is a list, while you are trying to use it as a tensor.
You could thus make sure that the forward method of your model returns a tensor or convert the list to a tensor using e.g. torch.stack.
Yes, Python lists don’t have the clone() or shape operations, which are PyTorch tensor ops, so it seems you are assuming feats is a tensor, while it’s a list.
Yes, the forward method seems to return a list, so you would have to check why this is the case (check the type of x and try to isolate where it’s transformed to a list) and/or create a tensor, if needed.