@utilities.remove_null_proxy_kwarg<EOL><INDENT>def get_objective_hierarchy_design_session(self):<DEDENT>
if not self.supports_objective_hierarchy_design():<EOL><INDENT>raise errors.Unimplemented()<EOL><DEDENT>return sessions.ObjectiveHierarchyDesignSession(runtime=self._runtime)<EOL>
Gets the session for designing objective hierarchies.

        return: (osid.learning.ObjectiveHierarchyDesignSession) - an
                ``ObjectiveHierarchyDesignSession``
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented -
                ``supports_objective_hierarchy_design()`` is ``false``
        *compliance: optional -- This method must be implemented if
        ``supports_objective_hierarchy_design()`` is ``true``.*