如何获得带有Alpakka且具有Commit Offset的Kafka批量大小的ConsumerRecord [String，String]列表？

Question

我需要从kafka获取记录，其批处理大小为Seq [ConsumerRecord [String，String]]，我创建了此示例代码，但对我不起作用

Consumer.committableSource(consumerSettings, Subscriptions.topics("topic-1"))
  .groupedWithin(10, 10.seconds)
  .mapAsync(1) { group =>
    val msgs =  group.toList.map(_.record.value())
    saveToDB(msgs )
  }
  .map(group => group.foldLeft(CommittableOffsetBatch.empty) { (batch, elem) => 
  batch.updated(elem.committableOffset) 
  })
  .mapAsync(3)(_.commitScaladsl()) 
  .runWith(Sink.ignore)

并编写saveToDB（msgs）函数

def saveToDB(msgs: List[String]):Future[Done] = ???

但无法正常工作，并且出现此错误

Error:(48, 25) value foldLeft is not a member of akka.Done
.map(group => group.foldLeft(CommittableOffsetBatch.empty) { (batch, elem) =>

如何编写将代码正确运行的saveToDB ???