@Override
  Map<String, String> fetchAccountMetadataFromZNRecord(ZNRecord record) {
    Map<String, String> result = record.getMapField(ACCOUNT_METADATA_MAP_KEY);
    if (result == null) {
      logger.info("ZNRecord={} to read on path={} does not have a simple map with key={}", record,
          FULL_ACCOUNT_METADATA_PATH, ACCOUNT_METADATA_MAP_KEY);
    }
    return result;
  }
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