docstr: Called at the end of an iteration.
  Subclasses should override for any actions to run. This function should only
  be called during TRAIN mode.
docstr_tok: ["Called","at","the","end","of","an","iteration",".","Subclasses","should","override","for","any","actions","to","run",".","This","function","should","only","be","called","during","TRAIN","mode","."]
code: def after_train_iter(self, runner):
      """
      Called at the end of an iteration.
      Subclasses should override for any actions to run. This function should only
      be called during TRAIN mode.
      """
      if self.by_epoch:
          return
  
      if self.every_n_iter(runner, self.interval):
          stats = {"iter": runner.global_step + 1}
          last_ckpt_path = self._format_checkpoint_name(
              dirname=self.dirname, filename=self.filename, stats=stats
          )
          runner.save_checkpoint(last_ckpt_path, self.save_weights_only)
  
file_path: BigDL/python/orca/src/bigdl/orca/learn/pytorch/callbacks/model_checkpoint.py
imports: from bigdl.orca.learn.pytorch.callbacks import Callback
  import os
  import re
  import warnings
  from bigdl.dllib.utils.log4Error import invalidInputError
label_desc: Use image node_id 3 for calling the ModelCheckpoint obj's underlying member method code with example usage: obj.after_train_iter(runner) without return types