Return the items which are tagged with a specific tag.
        When multiple tags are provided, they operate as "OR" query.

def tagged(self, *tag_slugs):
        """
        Return the items which are tagged with a specific tag.
        When multiple tags are provided, they operate as "OR" query.
        """
        if getattr(self.model, 'tags', None) is None:
            raise AttributeError("The {0} does not include TagsEntryMixin".format(self.model.__name__))

        if len(tag_slugs) == 1:
            return self.filter(tags__slug=tag_slugs[0])
        else:
            return self.filter(tags__slug__in=tag_slugs).distinct()