@abc.abstractmethod<EOL><INDENT>def get_gradebook_column_query_session(self):<DEDENT>
return<EOL>
Gets the ``OsidSession`` associated with the gradebook column query service.

        :return: a ``GradebookColumnQuerySession``
        :rtype: ``osid.grading.GradebookColumnQuerySession``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``Unimplemented`` -- ``supports_gradebook_column_query()`` is ``false``

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