local = Optional.absent();
      for (String currentValue : parameters.get(CHARSET_ATTRIBUTE)) {
        if (value == null) {
          value = currentValue;
          local = Optional.of(Charset.forName(value));
        } else if (!value.equals(currentValue)) {
          throw new IllegalStateException(
              "Multiple charset values defined: " + value + ", " + currentValue);
        }
      }