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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 find_rtr_namespace(self, rout_id):
 """Find the namespace associated with the router. """

        if rout_id is None:
            return None
        args = ['ip', 'netns', 'list']
        try:
            ns_list = utils.execute(args, root_helper=self.root_helper)
        except Exception as exc:
            LOG.error("Unable to find the namespace list Exception %s",
                      exc)
            return None
        for ns in ns_list.split():
            if 'router' in ns and rout_id in ns:
                return ns