code: public OperationFuture<List<Server>> addPublicIp(List<Server> servers, CreatePublicIpConfig publicIpConfig) {
          checkNotNull(servers, "Server list must be not null");
          checkNotNull(publicIpConfig, CHECK_PUBLIC_IP_CONFIG);
  
          List<JobFuture> futures = servers.stream()
              .map(serverRef -> addPublicIp(serverRef, publicIpConfig).jobFuture())
              .collect(toList());
  
          return new OperationFuture<>(
              servers,
              new ParallelJobsFuture(futures)
          );
      }
docs: Add public IP to list servers
  
  @param servers        servers reference list
  @param publicIpConfig publicIp config
  @return OperationFuture wrapper for list of ServerRef