How to use the alephclient.services.geoextract_pb2_grpc.GeoExtractStub function in alephclient

def analyze(self, document):
        if not document.supports_nlp or len(document.countries):
            return

        try:
            service = GeoExtractStub(self.channel)
            texts = self.text_iterator(document)
            countries = service.ExtractCountries(texts)
            for country in countries.countries:
                document.add_country(country)

            log.info("Countries [%s]: %r", document.id, document.countries)
        except self.Error as exc:
            log.exception("gRPC Error: %s", self.SERVICE)
            self.reset_channel()