class_docstr: Original BERT wordpiece tokenizer.
docstr: Beginning of sentence token id
docstr_tok: ["Beginning","of","sentence","token","id"]
code: def bos_token(self):
      """Beginning of sentence token id"""
      return self._bos_token
  
imports: from abc import ABC, abstractmethod
  from colossalai.legacy.context import ParallelMode
  from colossalai.legacy.core import global_context
  from .bert_tokenization import FullTokenizer
label_desc: Use image node_id 14 for calling the _BertWordPieceTokenizer obj's underlying member method code with example usage: obj.bos_token() and returns: self