code: static long parseDuration(String key, @Nullable String value) {
      requireArgument((value != null) && !value.isEmpty(), "value of key %s omitted", key);
      @SuppressWarnings("NullAway")
      String duration = value.substring(0, value.length() - 1);
      return parseLong(key, duration);
    }
docs: Returns a parsed duration value.