@abc.abstractmethod<EOL><INDENT>def get_activities_for_objective(self, objective_id):<DEDENT>
return<EOL>
Gets the activities for the given objective.

        In plenary mode, the returned list contains all of the
        activities mapped to the objective ``Id`` or an error results if
        an Id in the supplied list is not found or inaccessible.
        Otherwise, inaccessible ``Activities`` may be omitted from the
        list and may present the elements in any order including
        returning a unique set.

        :param objective_id: ``Id`` of the ``Objective``
        :type objective_id: ``osid.id.Id``
        :return: list of enrollments
        :rtype: ``osid.learning.ActivityList``
        :raise: ``NotFound`` -- ``objective_id`` not found
        :raise: ``NullArgument`` -- ``objective_id`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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