@abc.abstractmethod<EOL><INDENT>def get_catalog_assignment_session(self):<DEDENT>
return<EOL>
Gets the cataloging session for adding and removing mappings to catalogs.

        :return: a ``CatalogAssignmentSession``
        :rtype: ``osid.cataloging.CatalogAssignmentSession``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``Unimplemented`` -- ``supports_catalog_assignment()`` is ``false``

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