How to use the restless.exceptions.NotFound function in restless

def test_build_error(self):
        err = HttpError("Whoopsie")
        resp = self.res.build_error(err)
        resp_body = json.loads(resp.body)
        self.assertEqual(resp_body, {'error': 'Whoopsie'})
        self.assertEqual(resp.content_type, 'application/json')
        self.assertEqual(resp.status_code, 500)

        nf_err = NotFound()
        resp = self.res.build_error(nf_err)
        resp_body = json.loads(resp.body)
        # Default error message.
        self.assertEqual(resp_body, {'error': 'Resource not found.'})
        self.assertEqual(resp.content_type, 'application/json')
        # Custom status code.
        self.assertEqual(resp.status_code, 404)

        # Non-restless exception.
        unknown_err = AttributeError("'something' not found on the object.")
        resp = self.res.build_error(unknown_err)
        resp_body = json.loads(resp.body)
        # Still gets the JSON treatment & an appropriate status code.
        self.assertEqual(resp_body, {'error': "'something' not found on the object."})
        self.assertEqual(resp.content_type, 'application/json')
        self.assertEqual(resp.status_code, 500)

"""
        understood = (
            KeyError, ValueError, TypeError, AttributeError,
            SQLAlchemyError, DokomoError
        )

        if isinstance(err, tornado.web.HTTPError):
            restless_error = exc.HttpError(err.log_message)
            restless_error.status = err.status_code
            err = restless_error
        elif isinstance(err, SurveyAccessForbidden):
            restless_error = exc.HttpError(str(err))
            restless_error.status = 403
            err = restless_error
        elif isinstance(err, NoResultFound):
            err = exc.NotFound()
        elif isinstance(err, understood):
            err = exc.BadRequest(err)
        logging.exception(err)
        return super().handle_error(err)

def build_error(self, err):
        # A bit nicer behavior surrounding things that don't exist.
        if isinstance(err, (ObjectDoesNotExist, Http404)):
            err = NotFound(msg=six.text_type(err))

        return super(DjangoResource, self).build_error(err)

:param pk: ID of record

        Example:

            food = Food.get_or_404(1)
            food.name
            >>> Palmito 
            food.price
            >>> 10.9
        """
        obj = cls.query.get(pk)

        if obj:
            return obj
        else:
            raise NotFound()

food.name
        >>> CuzCuz

        # not found
        food = get_or_404(Food, 42)
        # { "error": "Food not found" }
    """
    if bind:
         obj = session.using(bind).query(_model).get(id)
    else:
        obj = session.query(_model).get(id)

    if obj:
        return obj
    else:
        raise NotFound('{0} not found'.format(_model.__name__))