@abc.abstractmethod<EOL><INDENT>def get_catalog_hierarchy_design_session(self, proxy):<DEDENT>
return<EOL>
Gets the catalog hierarchy design session.

        :param proxy: proxy
        :type proxy: ``osid.proxy.Proxy``
        :return: a ``CatalogHierarchyDesignSession``
        :rtype: ``osid.cataloging.CatalogHierarchyDesignSession``
        :raise: ``NullArgument`` -- ``proxy`` is null
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``Unimplemented`` -- ``supports_catalog_hierarchy_design()`` is ``false``

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