code: def end(self) -> None:
      assert self.start_time is not None
      self.duration += time() - self.start_time
      self.start_time = None
  
file_path: ColossalAI/examples/language/llama2/performance_evaluator.py
imports: from time import time
  from typing import Optional
  import torch
  import torch.distributed
  from torch import Tensor
  import colossalai.utils.device
  from colossalai.cluster import DistCoordinator
  from colossalai.utils.device import get_current_device
label_desc: Use image node_id 3 for calling the Timer obj's underlying member method code with example usage: obj.end() without return types