return key;
        }
        String keyStr = key.toString();
        if (keyStr.indexOf('_') < 0) {
            keyStr = CaseFormat.LOWER_CAMEL.to(CaseFormat.LOWER_UNDERSCORE, StringUtils.uncapitalize(keyStr));
        } else {
            keyStr = CaseFormat.LOWER_UNDERSCORE.to(CaseFormat.LOWER_CAMEL, keyStr);
        }
        return keyStr;
    }

    @Override
    public int size() {