code: def get_trainer_with_mock_updater(
      stop_trigger=(10, "iteration"), iter_per_epoch=10, extensions=None
  ):
      """Returns a :class:`~chainer.training.Trainer` object with mock updater.
  
      The returned trainer can be used for testing the trainer itself and the
      extensions. A mock object is used as its updater. The update function set
      to the mock correctly increments the iteration counts (
      ``updater.iteration``), and thus you can write a test relying on it.
  
      Args:
          stop_trigger: Stop trigger of the trainer.
          iter_per_epoch: The number of iterations per epoch.
          extensions: Extensions registered to the trainer.
  
      Returns:
          Trainer object with a mock updater.
  
      """
      if extensions is None:
          extensions = []
      check_available()
      updater = mock.Mock()
      updater.get_all_optimizers.return_value = {}
      updater.iteration = 0
      updater.epoch = 0
      updater.epoch_detail = 0
      updater.is_new_epoch = True
      updater.previous_epoch_detail = None
  
      def update():
          updater.update_core()
          updater.iteration += 1
          updater.epoch = updater.iteration // iter_per_epoch
          updater.epoch_detail = updater.iteration / iter_per_epoch
          updater.is_new_epoch = (
              updater.iteration - 1
          ) // iter_per_epoch != updater.epoch
          updater.previous_epoch_detail = (
              updater.iteration - 1
          ) / iter_per_epoch
  
      updater.update = update
      trainer = training.Trainer(
          updater, stop_trigger, extensions=extensions
      )
      return trainer
  
imports: from __future__ import division
  from chainer import training
label_desc: Use image node_id 4 for calling a global function with example usage: get_trainer_with_mock_updater(stop_trigger, iter_per_epoch, extensions) and returns: trainer