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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 keystone_configure_api_version(self, sentry_relation_pairs, deployment, api_version):
 """Configure preferred-api-version of keystone in deployment and monitor provided list of relation objects for propagation before returning to caller. :param sentry_relation_pairs: list of sentry, relation tuples used for monitoring propagation of relation data :param deployment: deployment to configure :param api_version: value preferred-api-version will be set to :returns: None if successful. Raise on error. """

        self.log.debug("Setting keystone preferred-api-version: '{}'"
                       "".format(api_version))

        config = {'preferred-api-version': api_version}
        deployment.d.configure('keystone', config)
        deployment._auto_wait_for_status()
        self.keystone_wait_for_propagation(sentry_relation_pairs, api_version)