code: def _extract_auth_config(self):
          
  
          service = self._service
          if not service.authentication:
              return {}
  
          auth_infos = {}
          for auth_rule in service.authentication.rules:
              selector = auth_rule.selector
              provider_ids_to_audiences = {}
              for requirement in auth_rule.requirements:
                  provider_id = requirement.providerId
                  if provider_id and requirement.audiences:
                      audiences = requirement.audiences.split(u",")
                      provider_ids_to_audiences[provider_id] = audiences
              auth_infos[selector] = AuthInfo(provider_ids_to_audiences)
          return auth_infos
docs: Obtains the authentication configurations.