code: def test_resumed_trigger_backward_compat(self):
      trainer = testing.get_trainer_with_mock_updater(
          stop_trigger=None, iter_per_epoch=self.iter_per_epoch
      )
      with tempfile.NamedTemporaryFile(delete=False) as f:
          trigger = training.triggers.OnceTrigger(self.call_on_resume)
          for expected, finished in zip(
              self.resumed_expected[: self.resume],
              self.resumed_finished[: self.resume],
          ):
              trainer.updater.update()
              self.assertEqual(trigger.finished, finished)
              self.assertEqual(trigger(trainer), expected)
          # old version does not save anything
          np.savez(f, dummy=0)
  
          trigger = training.triggers.OnceTrigger(self.call_on_resume)
          with testing.assert_warns(UserWarning):
              serializers.load_npz(f.name, trigger)
          for expected, finished in zip(
              self.resumed_expected[self.resume :],
              self.resumed_finished[self.resume :],
          ):
              trainer.updater.update()
              self.assertEqual(trigger.finished, finished)
              self.assertEqual(trigger(trainer), expected)
  
file_path: chainer/tests/chainer_tests/training_tests/triggers_tests/test_once_trigger.py
imports: from __future__ import division
  import random
  import tempfile
  import unittest
  import numpy
  from chainer import serializers
  from chainer import testing
  from chainer.testing import condition
  from chainer import training
label_desc: Use image node_id 6 for calling the TestOnceTrigger obj's underlying member method code with example usage: obj.test_resumed_trigger_backward_compat() without return types