@abc.abstractmethod<EOL><INDENT>def register_for_changed_comments_for_reference(self, reference_id):<DEDENT>
pass<EOL>
Register for notifications of changed comments for the given reference ``Id``.

        ``CommentReceiver.changedComments()`` is invoked when a
        ``Comment`` for the reference is changed.

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

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