@abc.abstractmethod<EOL><INDENT>def set_fixed_interval(self, interval):<DEDENT>
pass<EOL>
Sets the fixed interval.

        :param interval: the new fixed interval
        :type interval: ``osid.calendaring.Duration``
        :raise: ``InvalidArgument`` -- ``interval`` is invalid
        :raise: ``NoAccess`` -- ``interval`` cannot be modified
        :raise: ``NullArgument`` -- ``interval`` is ``null``

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