@abc.abstractmethod<EOL><INDENT>def changed_child_of_billings(self, notification_id, qualifier_ids):<DEDENT>
pass<EOL>
The callback for notifications of changes to children of qualifier hierarchy nodes.

        :param notification_id: the notification ``Id``
        :type notification_id: ``osid.id.Id``
        :param qualifier_ids: the ``Ids`` of the ``Qualifiers`` whose children have changed
        :type qualifier_ids: ``osid.id.IdList``


        *compliance: mandatory -- This method must be implemented.*