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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def ifdel(self, iff):
 """ removes all route entries that uses 'iff' interface. """

        new_routes = []
        for rt in self.routes:
            if rt[3] != iff:
                new_routes.append(rt)
        self.invalidate_cache()
        self.routes = new_routes