code: def before_train_epoch(self, runner):
      if self._is_rank_zero(runner):
          desc = "{}/{}e".format(runner.epochs + 1, runner.num_epochs)
  
          invalidInputError(
              tqdm is not None,
              "tqdm is not installed, please install with 'pip install tqdm'",
          )
          runner._progress_bar = tqdm(
              total=len(runner.train_loader),
              desc=desc,
              unit="batch",
              leave=False,
          )
  
file_path: BigDL/python/orca/src/bigdl/orca/learn/pytorch/callbacks/tqdm.py
imports: from bigdl.orca.learn.pytorch.callbacks import Callback
  from bigdl.dllib.utils.log4Error import invalidInputError
label_desc: Use image node_id 3 for calling the TqdmCallback obj's underlying member method code with example usage: obj.before_train_epoch(runner) without return types