@abc.abstractmethod<EOL><INDENT>def get_schedules(self):<DEDENT>
return<EOL>
Gets all ``Schedules``.

        In plenary mode, the returned list contains all known schedule
        or an error results. Otherwise, the returned list may contain
        only those schedule that are accessible through this session.

        :return: a ``ScheduleList``
        :rtype: ``osid.calendaring.ScheduleList``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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