code: def __init__(self, last_filename, checkpoint_dir="./", keep_last_n=0):
      self.last_filename = last_filename
      self.checkpoints = []
      self.checkpoint_dir = checkpoint_dir
      self.keep_last_n = keep_last_n
  
imports: import math
  import os
  import numpy
  import torch
  import shutil
  import signal
  import torch.distributed
label_desc: Use image node_id 1 to create a new Checkpointer object  with example: obj = Checkpointer(last_filename, checkpoint_dir, keep_last_n)