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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docstr: Calculate encoding using HuggingFace's RobertaTokenizerFast
  
  Parameters
  ----------
  datapoint: str
      Arbitrary string sequence to be tokenized.
  
  Returns
  -------
  encoding: List
      List containing three lists: the `input_ids`, 'token_type_ids', and `attention_mask`.
docstr_tok: ["Calculate","encoding","using","HuggingFace","'s","RobertaTokenizerFast","Parameters","--","--","--","--","--","datapoint",":","str","Arbitrary","string","sequence","to","be","tokenized",".","Returns","--","--","--","-","encoding",":","List","List","containing","three","lists",":","the","`","input_ids","`",",","'token_type_ids","'",",","and","`","attention_mask","`","."]
code: def _featurize(self, datapoint: str, **kwargs) -> List[List[int]]:
      """
      Calculate encoding using HuggingFace's RobertaTokenizerFast
  
      Parameters
      ----------
      datapoint: str
          Arbitrary string sequence to be tokenized.
  
      Returns
      -------
      encoding: List
          List containing three lists: the `input_ids`, 'token_type_ids', and `attention_mask`.
      """
  
      # the encoding is natively a dictionary with keys 'input_ids', 'token_type_ids', and 'attention_mask'
      encoding = list(self.tokenizer(datapoint, **kwargs).values())
      return encoding
  
imports: from deepchem.feat import Featurizer
  from typing import List
label_desc: Use image node_id 2 for calling the BertFeaturizer obj's underlying member method code with example usage: obj._featurize(datapoint) and returns: encoding