def str_from_int(func):
    """Function to be used as a decorator for a member method which
    returns some type convertible to `int` and accepts no arguments.
    The return value will be converted first to an `int` then to a
    `str` and is expanded with leading zeros on the left to be at least
    2 digits.
    """
    def wrapped(self):
        return str(int(func(self))).zfill(2)
    return wrapped