@Override
  ZKUpdater createNewZKUpdater(Collection<Account> accounts) {
    return new ZKUpdater(accounts);
  }
Constructor to create a {@link LegacyMetadataStore}.
@param accountServiceMetrics The metrics set to update metrics.
@param backupFileManager The {@link BackupFileManager} instance to manage backup files.
@param helixStore The {@link HelixPropertyStore} to fetch and update data.
ambry-account/src/main/java/com/github/ambry/account/LegacyMetadataStore.java