function findFields(locale) {
        var localeData = RelativeTimeFormat.__localeData__;
        var data = localeData[locale.toLowerCase()];
        // The locale data is de-duplicated, so we have to traverse the locale's
        // hierarchy until we find `fields` to return.
        while (data) {
            if (data.fields) {
                return data.fields;
            }
            data = data.parentLocale
                ? localeData[data.parentLocale.toLowerCase()]
                : undefined;
        }
        throw new Error("Locale data added to RelativeTimeFormat is missing 'fields' for \"" + locale + "\"");
    }
Find the correct field data in our CLDR data
@param locale locale