adds a version property to models implementing django-simple-history

history_helper.py

class HistoryHelperMixin(object):
    """ Adds a version property to models implementing django-simple-history
        https://github.com/treyhunner/django-simple-history
    """
    @property
    def version(self):
        return self.__class__._get_history_id(self.id)

    @classmethod
    def _get_history_id(cls, id):
        """ Gets the most recent history id column for the given class
        """
        if not getattr(cls, 'history', False):
            raise ValueError('Class does not have a history field')
        second_most_recent = cls.history.filter(id=id).order_by('-history_id').first()
        return second_most_recent.history_id + 1