@abc.abstractmethod<EOL><INDENT>def get_relationship_family_assignment_session(self):<DEDENT>
return<EOL>
Gets the ``OsidSession`` associated with assigning relationships to families.

        :return: a ``RelationshipFamilyAssignmentSession``
        :rtype: ``osid.relationship.RelationshipFamilyAssignmentSession``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``Unimplemented`` -- ``supports_relationship_family_assignment()`` is ``false``

        *compliance: optional -- This method must be implemented if
        ``supports_relationship_family_assignment()`` is ``true``.*