Returns attached container items and container configurations that are marked as persistent. Each returned
        item is in the format ``(config name, instance/attached name)``, where the instance name can also be ``None``.

        :return: Lists of attached items.
        :rtype: (list[(unicode | str, unicode | str)], list[unicode | str, unicode | str | NoneType])

def get_persistent_items(self):
        """
        Returns attached container items and container configurations that are marked as persistent. Each returned
        item is in the format ``(config name, instance/attached name)``, where the instance name can also be ``None``.

        :return: Lists of attached items.
        :rtype: (list[(unicode | str, unicode | str)], list[unicode | str, unicode | str | NoneType])
        """
        attached_items = [(container, ac)
                          for container, config in self
                          for ac in config.attaches]
        persistent_containers = [(container, ci)
                                 for container, config in self if config.persistent
                                 for ci in config.instances or [None]]
        return attached_items, persistent_containers