def METHOD_NAME(keys: str) -> Iterator[str]:
    while keys:
        special_key_match = cls.SPECIAL_KEY_RE.match(keys)
        if special_key_match is not None:
            special_key = special_key_match.group()
            yield special_key
            keys = keys[len(special_key) :]
        else:
            yield keys[0]
            keys = keys[1:]