code: def getAuthenticator(self, service_request):
          
          auth = service_request.service.getAuthenticator(service_request)
  
          if auth is None:
              return self.authenticator
  
          return auth
docs: Gets an authenticator callable based on the service_request. This is
          granular, looking at the service method first, then at the service
          level and finally to see if there is a global authenticator function
          for the gateway. Returns C{None} if one could not be found.