code: def run_ema_update_cpu(
      ema_model_tuple, current_model_tuple, decay, pre_sync_stream=None
  ):
      if pre_sync_stream is not None:
          pre_sync_stream.synchronize()
  
      ema_update(ema_model_tuple, current_model_tuple, decay)
  
imports: import contextlib
  import copy
  import os
  import threading
  from typing import Any, Dict, Iterable
  import pytorch_lightning
  import torch
  from pytorch_lightning import Callback
  from pytorch_lightning.utilities.exceptions import MisconfigurationException
  from pytorch_lightning.utilities.rank_zero import rank_zero_info
label_desc: Use image node_id 2 for calling a global function with example usage: run_ema_update_cpu(ema_model_tuple, current_model_tuple, decay, pre_sync_stream) without return types