class_docstr: Original BERT wordpiece tokenizer.
code: def add_token(self, token):
      if token not in self.vocab:
          self.inv_vocab[self.vocab_size] = token
          # self.vocab_size comes from len(vocab)
          # and it will increase as we add elements
          self.vocab[token] = self.vocab_size
  
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 2 for calling the _BertWordPieceTokenizer obj's underlying member method code with example usage: obj.add_token(token) without return types