def get_activities_by_record_type(self, activity_record_type=None):
raise Unimplemented()<EOL>
Gets a ActivityList containing the given activity record Type.
        In plenary mode, the returned list contains all known activities
        or an error results. Otherwise, the returned list may contain
        only those activities that are accessible through this session.
        arg:    activityRecordType (osid.type.Type): an activity record
                type
        return: (osid.learning.ActivityList) - the returned Activity
                list
        raise:  NullArgument - activityRecordType is null
        raise:  OperationFailed - unable to complete request
        raise:  PermissionDenied - authorization failure
        compliance: mandatory - This method must be implemented.