code: def __call__(self, trainer):
      # This is supposed to be called at the exact same interval
      # among all nodes
      if self.path is None:
          # Note: In a non-trainer use case this path will fail; You
          # shouldn't pass None at __init__().
          self.path = trainer.out
  
      self.save(trainer, trainer.updater.iteration)
  
imports: import errno
  import os
  import shutil
  import tempfile
  import time
  import warnings
  import chainer
  from chainer.training import extension
label_desc: Use image node_id 2 for calling the _MultiNodeCheckpointer obj's underlying member method code with example usage: obj.__call__(trainer) without return types