def get_revision(cls, id, revision, api=None):
        """
        Get app revision.
        :param id: App identifier.
        :param revision: App revision
        :param api: Api instance.
        :return: App object.
        """
        api = api if api else cls._API
        extra = {'resource': cls.__name__, 'query': {
            'id': id,
            'revision': revision
        }}
        logger.info('Get revision', extra=extra)
        app = api.get(url=cls._URL['get_revision'].format(
            id=id, revision=revision)).json()
        return App(api=api, **app)
Get app revision.
        :param id: App identifier.
        :param revision: App revision
        :param api: Api instance.
        :return: App object.