@abc.abstractmethod<EOL><INDENT>def update_recurring_event(self, recurring_event_form):<DEDENT>
pass<EOL>
Updates an existing recurring event.

        :param recurring_event_form: the form containing the elements to be updated
        :type recurring_event_form: ``osid.calendaring.RecurringEventForm``
        :raise: ``IllegalState`` -- ``recurring_event_form`` already used in an update transaction
        :raise: ``InvalidArgument`` -- the form contains an invalid value
        :raise: ``NullArgument`` -- ``recurring_event_form`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure
        :raise: ``Unsupported`` -- ``recurring_event_form`` did not originate in an update transaction

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