@abc.abstractmethod<EOL><INDENT>def register_for_new_relationships(self):<DEDENT>
pass<EOL>
Register for notifications of new relationships.

        ``RelationshipReceiver.newRelationships()`` is invoked when a
        new ``Relationship`` appears in this family.

        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

        *compliance: mandatory -- This method must be implemented.*