old_contents: from chainer.training import extension  # NOQA
  from chainer.training import extensions # NOQA
  from chainer.training import trainer  # NOQA
  from chainer.training import trigger  # NOQA
  from chainer.training import triggers  # NOQA
  from chainer.training import updater  # NOQA
  from chainer.training import updaters  # NOQA
  from chainer.training import util  # NOQA
  
  
  # import class and function
  from chainer.training.extension import Extension  # NOQA
  from chainer.training.extension import make_extension  # NOQA
  from chainer.training.extension import PRIORITY_EDITOR  # NOQA
  from chainer.training.extension import PRIORITY_READER  # NOQA
  from chainer.training.extension import PRIORITY_WRITER  # NOQA
  from chainer.training.trainer import Trainer  # NOQA
  from chainer.training.trigger import get_trigger  # NOQA
  from chainer.training.trigger import IntervalTrigger  # NOQA
  from chainer.training.updater import ParallelUpdater  # NOQA
  from chainer.training.updater import StandardUpdater  # NOQA
  from chainer.training.updater import Updater  # NOQA
  
new_contents: from chainer.training import extension  # NOQA
  from chainer.training import extensions  # NOQA
  from chainer.training import trainer  # NOQA
  from chainer.training import trigger  # NOQA
  from chainer.training import triggers  # NOQA
  from chainer.training import updater  # NOQA
  from chainer.training import updaters  # NOQA
  from chainer.training import util  # NOQA
  
  
  # import class and function
  from chainer.training.extension import Extension  # NOQA
  from chainer.training.extension import make_extension  # NOQA
  from chainer.training.extension import PRIORITY_EDITOR  # NOQA
  from chainer.training.extension import PRIORITY_READER  # NOQA
  from chainer.training.extension import PRIORITY_WRITER  # NOQA
  from chainer.training.trainer import Trainer  # NOQA
  from chainer.training.trigger import get_trigger  # NOQA
  from chainer.training.trigger import IntervalTrigger  # NOQA
  from chainer.training.updater import ParallelUpdater  # NOQA
  from chainer.training.updater import StandardUpdater  # NOQA
  from chainer.training.updater import Updater  # NOQA
  
subject: Fix flake8