src/transformers/models/transfo_xl/tokenization_transfo_xl.py/LMMultiFileIterator/__iter__
class LMMultiFileIterator:    def __iter__(self):
        if self.shuffle:
            np.random.shuffle(self.paths)

        for path in self.paths:
            # sent_stream is an iterator
            sent_stream = self.get_sent_stream(path)
            for batch in self.stream_iterator(sent_stream):
                yield batch