docs: private Optional<Long> getLongValue(String path) {
  
          String stringValue = getStringValue(path);
          if (stringValue == null) {
              return Optional.absent();
          } else {
              try {
                  return Optional.<Long> of(Long.valueOf(stringValue.trim()));
              } catch (NumberFormatException e) {
                  throw new NumberFormatException("Could not read a number from " + path + " ,value= " + stringValue);
              }
          }
      }