def count_sents(self, sents, verbose=False):
        """
        sents : a list of sentences, each a list of tokenized symbols
        """
        if verbose:
            logger.info(f"counting {len(sents)} sents ...")
        for idx, symbols in enumerate(sents):
            if verbose and idx > 0 and idx % 500000 == 0:
                logger.info(f"    line {idx}")
            self.counter.update(symbols)

        sents : a list of sentences, each a list of tokenized symbols
        
dpkd/transformers/src/transformers/models/transfo_xl/tokenization_transfo_xl.py