public Collection<String> viewAccountMetadata(int version) {
    Map<String, String> accountMetadata = routerStore.fetchAccountMetadataAtVersion(version);
    if (accountMetadata != null) {
      return accountMetadata.values();
    } else {
      return null;
    }
  }
Fetch the {@link Account} metadata at given version and return their json format as a collection of String.
Or null whenever there is an error.
@param version The version to fetch the {@link Account} metadata.
@return A collection of json string of {@link Account} metadata.
ambry-tools/src/main/java/com/github/ambry/account/AccountTool.java