human
Complete this python program:
def exhaust(rule):
assistant
#Here is the Python program you requested.

    """Apply a rule repeatedly until it has no effect
    """
    def exhaustive_rl(expr):
        (new, old) = (rule(expr), expr)
        while (new != old):
            (new, old) = (rule(new), new)
        return new
    return exhaustive_rl