code: def save(self, filename="databunch.pkl"):
      tmp_path = self.data_dir / "tmp"
      tmp_path.mkdir(exist_ok=True)
      with open(str(tmp_path / filename), "wb") as f:
          pickle.dump(self, f)
  
imports: import pandas
  import os
  import torch
  from pathlib import Path
  import pickle
  from torch.utils.data import TensorDataset, DataLoader, RandomSampler, SequentialSampler
  from torch.utils.data.distributed import DistributedSampler
  from transformers import WEIGHTS_NAME, BertConfig, BertForSequenceClassification, BertTokenizer, XLMConfig, XLMForSequenceClassification, XLMTokenizer, XLNetConfig, XLNetForSequenceClassification, XLNetTokenizer
label_desc: Use image node_id 2 for calling the BertDataBunch obj's underlying member method code with example usage: obj.save(filename) without return types