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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_activities_for_objective(self, objective_id):
 """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. arg: objective_id (osid.id.Id):
 ``Id`` of the ``Objective`` return: (osid.learning.ActivityList) - list of enrollments 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.* """

        # Implemented from template for
        # osid.learning.ActivityLookupSession.get_activities_for_objective_template
        # NOTE: This implementation currently ignores plenary view
        collection = JSONClientValidated('learning',
                                         collection='Activity',
                                         runtime=self._runtime)
        result = collection.find(
            dict({'objectiveId': str(objective_id)},
                 **self._view_filter()))
        return objects.ActivityList(result, runtime=self._runtime)