def get_relationships_by_ids(self, relationship_ids):
        """Gets a ``RelationshipList`` corresponding to the given ``IdList``.

        arg:    relationship_ids (osid.id.IdList): the list of ``Ids``
                to retrieve
        return: (osid.relationship.RelationshipList) - the returned
                ``Relationship list``
        raise:  NotFound - an ``Id`` was not found
        raise:  NullArgument - ``relationship_ids`` is ``null``
        raise:  OperationFailed - unable to complete request
        raise:  PermissionDenied - authorization failure
        *compliance: mandatory -- This method must be implemented.*

        """
        # Implemented from template for
        # osid.resource.ResourceLookupSession.get_resources_by_ids
        # NOTE: This implementation currently ignores plenary view
        collection = JSONClientValidated('relationship',
                                         collection='Relationship',
                                         runtime=self._runtime)
        object_id_list = []
        for i in relationship_ids:
            object_id_list.append(ObjectId(self._get_id(i, 'relationship').get_identifier()))
        result = collection.find(
            dict({'_id': {'$in': object_id_list}},
                 **self._view_filter()))
        result = list(result)
        sorted_result = []
        for object_id in object_id_list:
            for object_map in result:
                if object_map['_id'] == object_id:
                    sorted_result.append(object_map)
                    break
        return objects.RelationshipList(sorted_result, runtime=self._runtime, proxy=self._proxy)
Gets a ``RelationshipList`` corresponding to the given ``IdList``.

        arg:    relationship_ids (osid.id.IdList): the list of ``Ids``
                to retrieve
        return: (osid.relationship.RelationshipList) - the returned
                ``Relationship list``
        raise:  NotFound - an ``Id`` was not found
        raise:  NullArgument - ``relationship_ids`` is ``null``
        raise:  OperationFailed - unable to complete request
        raise:  PermissionDenied - authorization failure
        *compliance: mandatory -- This method must be implemented.*