docs: def get_gradebook_admin_session(self, proxy):
          """Gets the OsidSession associated with the gradebook administration service.
  
          arg:    proxy (osid.proxy.Proxy): a proxy
          return: (osid.grading.GradebookAdminSession) - a
                  ``GradebookAdminSession``
          raise:  NullArgument - ``proxy`` is ``null``
          raise:  OperationFailed - unable to complete request
          raise:  Unimplemented - ``supports_gradebook_admin() is false``
          *compliance: optional -- This method must be implemented if
          ``supports_gradebook_admin()`` is true.*
  
          """
          if not self.supports_gradebook_admin():
              raise errors.Unimplemented()
          # pylint: disable=no-member
          return sessions.GradebookAdminSession(proxy=proxy, runtime=self._runtime)