question: How to save/load only part of the weights in the model?
context: For example, part of my model's parameters are frozen, no need to train, no need to save
answer: This might work:
  def on_save_checkpoint(checkpoint):
      # pop the backbone here using custom logic
      del checkpoint['state_dict'][backbone_keys]
  
  LitModel.load_from_checkpoint(ckpt_path, strict=False)