@abc.abstractmethod<EOL><INDENT>def get_activities_for_objectives(self, objective_ids):<DEDENT>
return<EOL>
Gets the activities for the given objectives.

        In plenary mode, the returned list contains all of the
        activities specified in the objective ``Id`` list, in the order
        of the list, including duplicates, or an error results if a
        course offering ``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_ids: list of objective ``Ids``
        :type objective_ids: ``osid.id.IdList``
        :return: list of activities
        :rtype: ``osid.learning.ActivityList``
        :raise: ``NotFound`` -- an ``objective_id`` not found
        :raise: ``NullArgument`` -- ``objective_id_list`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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