private Pair<Set<String>, Set<String>> getWritablePartitions() {
    Set<String> writableInClusterManager = new HashSet<>();
    for (PartitionId partition : clusterManager.getWritablePartitionIds(null)) {
      String partitionStr = partition.toPathString();
      writableInClusterManager.add(partitionStr);
    }
    Set<String> writableInCluster = helixCluster.getWritablePartitions();
    if (writableInCluster.isEmpty()) {
      writableInCluster = helixCluster.getAllWritablePartitions();
    }
    return new Pair<>(writableInCluster, writableInClusterManager);
  }
Get the writable partitions returned by the {@link HelixClusterManager} as well as those in helix cluster.
@return two writable partition sets from helix cluster and {@link HelixClusterManager}.
ambry-clustermap/src/test/java/com/github/ambry/clustermap/HelixClusterManagerTest.java