human
Complete this python program:
def do_one(*rules):
assistant
#Here is the Python program you requested.

    """Try each of the rules until one works. Then stop.
    """
    def do_one_rl(expr):
        for rl in rules:
            result = rl(expr)
            if (result != expr):
                return result
        return expr
    return do_one_rl