class_docstr: Bert Featurizer.
  
  Bert Featurizer.
  The Bert Featurizer is a wrapper class for HuggingFace's BertTokenizerFast.
  This class intends to allow users to use the BertTokenizer API while
  remaining inside the DeepChem ecosystem.
  
  Examples
  --------
  >>> from deepchem.feat import BertFeaturizer
  >>> from transformers import BertTokenizerFast
  >>> tokenizer = BertTokenizerFast.from_pretrained("Rostlab/prot_bert", do_lower_case=False)
  >>> featurizer = BertFeaturizer(tokenizer)
  >>> feats = featurizer.featurize(['D L I P [MASK] L V T'])
  
  Notes
  -----
  Examples are based on RostLab's ProtBert documentation.
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code: def __init__(self, tokenizer: BertTokenizerFast):
      if not isinstance(tokenizer, BertTokenizerFast):
          raise TypeError(
              f"""`tokenizer` must be a constructed `BertTokenizerFast`
                  object, not {type(tokenizer)}"""
          )
      else:
          self.tokenizer = tokenizer
  
imports: from deepchem.feat import Featurizer
  from typing import List
label_desc: Use image node_id 1 to create a new BertFeaturizer object from inherited base classes: Featurizer with example: obj = BertFeaturizer(tokenizer)