def get_relationships_for_peers(self, source_id=None, destination_id=None):
raise Unimplemented()<EOL>
Gets a ``RelationshipList`` corresponding to the given peer ``Ids``.

        arg:    source_id (osid.id.Id): a peer ``Id``
        arg:    destination_id (osid.id.Id): a related peer ``Id``
        return: (osid.relationship.RelationshipList) - the relationships
        raise:  NullArgument - ``source_id`` or ``destination_id`` is
                ``null``
        raise:  OperationFailed - unable to complete request
        raise:  PermissionDenied - authorization failure
        *compliance: mandatory -- This method must be implemented.*