old_contents: from chainer.serializers import npz
  from chainer.trainer import extension
  
  
  def snapshot(savefun=npz.save_npz,
               filename='snapshot_iter_{.updater.iteration}'):
      """Return a trainer extension to take snapshots of the trainer.
  
      This extension serializes the trainer object and saves it to the output
      directory. It is used to support resuming the training loop from the saved
      state.
  
      This extension is called once for each epoch by default.
  
      .. note::
         This extension first writes the serialized object to a temporary file
         and then rename it to the target file name. Thus, if the program stops
         right before the renaming, the temporary file might be left in the
         output directory.
  
      Args:
          savefun: Function to save the trainer. It takes two arguments: the
              output file path and the trainer object.
          filename (str): Name of the file into which the trainer is serialized.
              It can be a format string, where the trainer object is passed to
              the :meth:`str.format` method.
  
      """
      @extension.make_extension(trigger=(1, 'epoch'))
      def ext(trainer):
          fname = filename.format(trainer)
          fd, tmppath = tempfile.mkstemp(prefix=fname, dir=trainer.out)
          try:
              savefun(tmppath, trainer)
          finally:
              os.close(fd)
          os.rename(tmppath, os.path.join(trainer.out, fname))
  
      return ext
  
new_contents: from chainer.serializers import npz
  from chainer.trainer import extension
  
  
  def snapshot(savefun=npz.save_npz,
               filename='snapshot_iter_{.updater.iteration}'):
      """Return a trainer extension to take snapshots of the trainer.
  
      This extension serializes the trainer object and saves it to the output
      directory. It is used to support resuming the training loop from the saved
      state.
  
      This extension is called once for each epoch by default.
  
      .. note::
         This extension first writes the serialized object to a temporary file
         and then rename it to the target file name. Thus, if the program stops
         right before the renaming, the temporary file might be left in the
         output directory.
  
      Args:
          savefun: Function to save the trainer. It takes two arguments: the
              output file path and the trainer object.
          filename (str): Name of the file into which the trainer is serialized.
              It can be a format string, where the trainer object is passed to
              the :meth:`str.format` method.
  
      """
      @extension.make_extension(name='snapshot', trigger=(1, 'epoch'))
      def ext(trainer):
          fname = filename.format(trainer)
          fd, tmppath = tempfile.mkstemp(prefix=fname, dir=trainer.out)
          try:
              savefun(tmppath, trainer)
          finally:
              os.close(fd)
          os.rename(tmppath, os.path.join(trainer.out, fname))
  
      return ext
  
subject: Add name to the snapshot extension