function isValidLocaleDefinition(locale) {
        return (
            typeof locale == 'object' &&
            REQUIRED_LOCALE_DEFINITION_KEYS.every(localeKey => locale.hasOwnProperty(localeKey))
        );
    }
Checks if a locale definition object contains the required keys
@param  {LocaleObject}  locale   Locale to check
@return {Boolean}                Is the locale definition has a correct format (https://cdn.jsdelivr.net/npm/d3-format/locale/en-US.json)