def _build_header(self, raw_msg, raw_headers):

        header1 = SubscriberEndpointUnit._build_header(self, raw_msg, raw_headers)
        header2 = ProcessEndpointUnitMixin._build_header(self, raw_msg, raw_headers)

        header1.update(header2)

        return header1
Override to direct the calls in _build_header - first the Subscriber, then the Process mixin.
dataset/ETHPy150Open ooici/pyon/pyon/ion/endpoint.py/ProcessSubscriberEndpointUnit._build_header