human
Complete the below
def exhaust(rule):

    ''''Apply a rule repeatedly until it has no effect'
    '''

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Give me a the Python code you requested?
assistant
#Here is the Python code you requested.
    def exhaustive_rl(expr):
        (new, old) = (rule(expr), expr)
        while (new != old):
            (new, old) = (rule(new), new)
        return new
    return exhaustive_rl