@abc.abstractmethod<EOL><INDENT>def get_blackouts(self):<DEDENT>
return<EOL>
Gets the blackout dates for this recurring event.

        Recurring events overlapping with the time intervals do not
        appear in their series.

        :return: recurring event exceptions
        :rtype: ``osid.calendaring.DateTimeIntervalList``

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