code: function localizer( languageTag, optionalFallback ) {
  
        // eslint-disable-next-line valid-jsdoc
        /**
         * @name Localizer
         * @private
         */
        function partial( i18nValue ) {
           return localize( languageTag, i18nValue, optionalFallback );
        }
  
        /**
         * Shortcut to string.format, for simple chaining to the localizer.
         *
         * These are equal:
         * - `string.format( i18n.localizer( tag )( i18nValue ), numericArgs, namedArgs )`
         * - `i18n.localizer( tag ).format( i18nValue, numericArgs, namedArgs )`.
         *
         * @param {String} i18nValue
         *    the value to localize and then format
         * @param {Array} [optionalIndexedReplacements]
         *    replacements for any numeric placeholders in the localized value
         * @param {Object} [optionalNamedReplacements]
         *    replacements for any named placeholders in the localized value
         *
         * @return {String}
         *    the formatted string, taking i18n into account
         *
         * @memberOf Localizer
         */
        partial.format = function( i18nValue, optionalIndexedReplacements, optionalNamedReplacements ) {
           const formatString = localize( languageTag, i18nValue );
           if( formatString === undefined ) {
              return optionalFallback;
           }
           return format( formatString, optionalIndexedReplacements, optionalNamedReplacements );
        };
  
        return partial;
     }
docs: ///////////////////////////////////////////////////////////////////////////////////////////////////////// 
  Encapsulate a given languageTag in a partially applied localize function.
  
  @param {String} languageTag
  the languageTag to lookup localizations with
  @param {*} [optionalFallback]
  a value to use by the localizer function whenever no localization is available for the language tag
  
  @return {Localizer}
  A single-arg localize-Function, which always uses the given language-tag. It also has a `.format`
  -method, which can be used as a shortcut to `string.format( localize( x ), args )`