src/transformers/models/ctrl/tokenization_ctrl.py/CTRLTokenizer/_tokenize
class CTRLTokenizer:    def _tokenize(self, text):
        """Tokenize a string."""
        split_tokens = []

        words = re.findall(r"\S+\n?", text)

        for token in words:
            split_tokens.extend([t for t in self.bpe(token).split(" ")])
        return split_tokens