code: def _filenames(self, iterations):
      return [self._filename(i) for i in iterations]
  
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 7 for calling the _MultiNodeCheckpointer obj's underlying member method code with example usage: obj._filenames(iterations) and returns: unknown