src/transformers/models/gpt2/modeling_gpt2.py/GPT2LMHeadModel/deparallelize
class GPT2LMHeadModel:    def deparallelize(self):
        self.transformer.deparallelize()
        self.transformer = self.transformer.to("cpu")
        self.lm_head = self.lm_head.to("cpu")
        self.model_parallel = False
        torch.cuda.empty_cache()