def get_root_objectives(self):
<EOL>root_ids = self._hierarchy_session.get_roots()<EOL>collection = JSONClientValidated('<STR_LIT>',<EOL>collection='<STR_LIT>',<EOL>runtime=self._runtime)<EOL>result = collection.find(<EOL>dict({'<STR_LIT>': {'<STR_LIT>': [ObjectId(root_id.get_identifier()) for root_id in root_ids]}},<EOL>**self._view_filter()))<EOL>return objects.ObjectiveList(<EOL>result,<EOL>runtime=self._runtime,<EOL>proxy=self._proxy)<EOL>
Gets the root objective in this objective hierarchy.

        return: (osid.learning.ObjectiveList) - the root objective
        raise:  OperationFailed - unable to complete request
        raise:  PermissionDenied - authorization failure
        *compliance: mandatory -- This method is must be implemented.*