@classmethod
def sort(cls):
    """
        Sort the items by their value.

        Used for example by :mod:`lino_xl.lib.orders` where we add a journal
        group to :class:`lino_xl.lib.ledger.JournalGroups` and want it to come
        before the other groups.

        """
    cls.choices.sort(key=lambda x: x[0].value)
