rxjs6管道两个可观察到的给出订阅不是功能

Question

rxjs 6.2.1

我得到ClusterStreams__.a.subscribe is not a function

我正在尝试使用以下代码将getClusterArns()的结果传输到describeClusters()中……

function getClusterArns() {
        const ecs = new AWS.ECS();
        return ecs.listClusters().promise();
}

function describeClusters(clusterArns) {
    const params = { clusters: clusterArns };
        const ecs = new AWS.ECS();
        return ecs.describeClusters(params).promise();
}


export const ClusterArnStream = from(getClusterArns());
export const ClusterStream = pipe(
  combineLatest(ClusterArnStream),
  mergeMap(([_, clusterArnsResponse]) => describeClusters(clusterArnsResponse.clusterArns)),
  map(x => x.clusters),
  multicast(() => new ReplaySubject(1))
);