def __init__(self, do_lower_case=True, never_split=("[UNK]", "[SEP]", "[PAD]", "[CLS]", "[MASK]")):
        """Constructs a BasicTokenizer.

        Args:
          do_lower_case: Whether to lower case the input.
        """
        self.do_lower_case = do_lower_case
        self.never_split = never_split
Constructs a BasicTokenizer.

        Args:
          do_lower_case: Whether to lower case the input.
        
unilm-v1/src/pytorch_pretrained_bert/tokenization.py