@abc.abstractmethod<EOL><INDENT>def register_for_changed_calendar_hierarchy_for_ancestors(self, calendar_id):<DEDENT>
pass<EOL>
Calendar ``Receiver.

        changedChildOfCalendars()`` is invoked when the specified node
        or any of its ancestors experiences a change in its children.

        :param calendar_id: the ``Id`` of the ``Calendar`` node to monitor
        :type calendar_id: ``osid.id.Id``
        :raise: ``NullArgument`` -- ``calendar_id`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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