How to retrieve the class names of a trained ResNet?

I have a model that I trained around a year ago, and now when I try to make predictions, I can’t retrieve the names of the classes so I don’t know which class does it refer to.

def predict_image(img, model):
    # Convert to a batch of 1
    device = torch.device('cpu')
    xb = to_device(img.unsqueeze(0), device)
    # Get predictions from model
    yb = model(xb)
    # Pick index with highest probability
    _, preds  = torch.max(yb, dim=1)
    # Retrieve the class label
    return train_ds.classes[preds[0].item()]

I have no access to train_ds