Set<String> getAllWritablePartitions() {
    Set<String> writablePartitions = new HashSet<>();
    for (Map.Entry<String, Set<String>> entry : partitionToInstances.entrySet()) {
      if (!partitionToPartitionStates.get(entry.getKey()).equals(PartitionState.READ_ONLY)) {
        writablePartitions.add(entry.getKey());
      }
    }
    return writablePartitions;
  }
@return all writable partitions registered via this Helix admin.
ambry-clustermap/src/test/java/com/github/ambry/clustermap/MockHelixAdmin.java