@Override
  public List<String> getSealedReplicas() {
    // TODO refactor these getter methods to return set instead of list.
    return new ArrayList<>(getDataNodeConfig().getSealedReplicas());
  }
@return list of sealed replicas from HelixAdmin.
ambry-clustermap/src/main/java/com/github/ambry/clustermap/HelixParticipant.java