@abc.abstractmethod<EOL><INDENT>def assign_gradebook_column_to_gradebook(self, gradebook_column_id, gradebook_id):<DEDENT>
pass<EOL>
Adds an existing ``GradebookColumn`` to a ``Gradebook``.

        :param gradebook_column_id: the ``Id`` of the ``GradebookColumn``
        :type gradebook_column_id: ``osid.id.Id``
        :param gradebook_id: the ``Id`` of the ``Gradebook``
        :type gradebook_id: ``osid.id.Id``
        :raise: ``AlreadyExists`` -- ``gradebook_column_id`` is already assigned to ``gradebook_id``
        :raise: ``NotFound`` -- ``gradebook_column_id`` or ``gradebook_id`` not found
        :raise: ``NullArgument`` -- ``gradebook_column_id`` or ``gradebook_id`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

        *compliance: mandatory -- This method must be implemented.*