code: public static String getQualifierNamespace(String qualifierAsString) {
      int pos = qualifierAsString.indexOf(DELIMITER, 1);
      if (pos == -1) {
        throw new IllegalArgumentException("Wrong qualifier format: '" + qualifierAsString + "'");
      }
      return qualifierAsString.substring(1, pos);
    }
docs: Extracts qualifier namespace part from given qualifier string.
  
  @param qualifierAsString qualifier string.
  @return qualifier namespace.