code: public static Optional<String> getBranchIdentifier(IBAN iban) {
          return Optional.ofNullable(IBANFieldsCompat.getBranchIdentifier(iban));
      }
docs: Returns the branch identifier from the given IBAN, if available.
  @param iban an iban to evaluate. Cannot be null.
  @return the branch ID for this IBAN, or <code>EMPTY</code> if unknown.