def wall_comments(self):
        if 'vkontakte_wall' not in settings.INSTALLED_APPS:
            raise ImproperlyConfigured("Application 'vkontakte_wall' not in INSTALLED_APPS")

        from vkontakte_wall.models import Comment
        # TODO: improve schema and queries with using owner_id field
        return Comment.objects.filter(remote_id__startswith='-%s_' % self.remote_id)