@abc.abstractmethod<EOL><INDENT>def get_exceptions(self):<DEDENT>
return<EOL>
Gets the exceptions to this time period.

        Recurring events overlapping with these events do not appear in
        any recurring event for this time period.

        :return: event exceptions
        :rtype: ``osid.calendaring.EventList``
        :raise: ``OperationFailed`` -- unable to complete request

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