@abc.abstractmethod<EOL><INDENT>def get_grade_system_admin_session_for_gradebook(self, gradebook_id, proxy):<DEDENT>
return<EOL>
Gets the ``OsidSession`` associated with the grade system admin service for the given gradebook.

        :param gradebook_id: the ``Id`` of the gradebook
        :type gradebook_id: ``osid.id.Id``
        :param proxy: a proxy
        :type proxy: ``osid.proxy.Proxy``
        :return: ``a GradeSystemAdminSession``
        :rtype: ``osid.grading.GradeSystemAdminSession``
        :raise: ``NotFound`` -- ``gradebook_id`` not found
        :raise: ``NullArgument`` -- ``gradebook_id`` or ``proxy`` is ``null``
        :raise: ``OperationFailed`` -- ``unable to complete request``
        :raise: ``Unimplemented`` -- ``supports_grade_system_admin()`` or ``supports_visible_federation()`` is ``false``

        *compliance: optional -- This method must be implemented if
        ``supports_grade_system_admin()`` and
        ``supports_visible_federation()`` are ``true``.*