code: def _setdefault(self, key, default=None):
          
          return self.connection.retry(self.__inner_set_default, key, default)
docs: If ``key`` is not present, set it as ``default`` and return it.  If
          ``key`` is present, return its value.
  
          :param key: Key to add to Zookeeper
          :type key: string
          :param default: Default object to return if ``key`` is present.
          :type default: object
  
          Will retry trying to get or create a node based on the "retry" config
          from the Kazoo client.