docs: @Override
      public List<ServiceInstance> lookupInstances(String serviceName)
              throws ServiceException {
          if(! isStarted){
              ServiceDirectoryError error = new ServiceDirectoryError(ErrorCode.SERVICE_DIRECTORY_MANAGER_FACTORY_CLOSED);
              throw new ServiceException(error);
          }
  
          List<ModelServiceInstance> modelSvc = getLookupService().getUPModelInstances(serviceName);
          if(modelSvc == null || modelSvc.isEmpty()){
              return Collections.emptyList();
          }else{
              List<ServiceInstance> instances = new ArrayList<ServiceInstance>();
              for(ModelServiceInstance modelInstance : modelSvc){
                  instances.add(ServiceInstanceUtils.transferFromModelServiceInstance(modelInstance));
              }
              return instances;
          }
      }