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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 add_url_rule(self, host, rule_string, endpoint, **options):
 """Add a url rule to the app instance. The url rule is the same with Flask apps and other Werkzeug apps. :param host: the matched hostname. e.g. "www.python.org" :param rule_string: the matched path pattern. e.g. "/news/<int:id>" :param endpoint: the endpoint name as a dispatching key such as the qualified name of the object. """

        rule = Rule(rule_string, host=host, endpoint=endpoint, **options)
        self.url_map.add(rule)