code: def vocab_size(self):
      return self._vocab_size
  
imports: import os
  from typing import Tuple, List
  import mxnet
  from mxnet import use_np
  from mxnet.gluon import nn
  from .base import BACKBONE_REGISTRY
  from .transformer import TransformerModel
  from ..base import get_model_zoo_home_dir, get_repo_model_zoo_url, get_model_zoo_checksum_dir
  from ..utils.misc import download, load_checksum_stats
  from ..utils.config import CfgNode
  from ..utils.registry import Registry
  from ..data.tokenizers import HuggingFaceByteBPETokenizer
label_desc: Use image node_id 5 for calling the BartModel obj's underlying member method code with example usage: obj.vocab_size() and returns: self