def iterorderable(self):
        return (x for x in self.iterall() if x.orderable)
CORS Specification Section 6.2.4, 6.2.6
dataset/ETHPy150Open bradleyayers/django-tables2/django_tables2/columns/base.py/BoundColumns.iterorderable--crossover with--dataset/ETHPy150Open openstack/oslo.middleware/oslo_middleware/tests/test_cors.py/CORSPreflightRequestTest.test_request_headers_not_permitted