code: def __call__(self, epoch, backbone, opt_backbone):
      if self.rank == 0:
          path_module = os.path.join(
              self.output, "backbone_ep%04d.pth" % epoch
          )
          if self.save_opt:
              data = {
                  "model": backbone.module.state_dict(),
                  "optimizer": opt_backbone.state_dict(),
              }
          else:
              data = backbone.module.state_dict()
          torch.save(data, path_module)
          logging.info(
              "Pytorch Model Saved in '{}'".format(path_module)
          )
  
imports: import logging
  import os
  import time
  from typing import List
  import torch
  import psutil
  from utils.utils_logging import AverageMeter
label_desc: Use image node_id 2 for calling the CallBackModelCheckpoint obj's underlying member method code with example usage: obj.__call__(epoch, backbone, opt_backbone) without return types