code: function localizeStrict( languageTag, i18nValue, optionalFallback ) {
        assert( languageTag ).hasType( String );
        if( !i18nValue || primitives[ typeof i18nValue ] ) {
           // Value is not i18n
           return i18nValue;
        }
        assert( languageTag ).isNotNull();
  
        // Try one direct lookup before scanning the input keys,
        // assuming that language-tags are written in consistent style.
        const value = i18nValue[ languageTag ];
        if( value !== undefined ) {
           return value;
        }
  
        const lookupKey = normalize( languageTag );
        const availableTags = keys( i18nValue );
        const n = availableTags.length;
        for( let i = 0; i < n; ++i ) {
           const t = availableTags[ i ];
           if( normalize( t ) === lookupKey ) {
              return i18nValue[ t ];
           }
        }
  
        return optionalFallback;
     }
docs: ///////////////////////////////////////////////////////////////////////////////////////////////////////// 
  Localize the given internationalized object using the given languageTag.
  
  @param {String} languageTag
  the languageTag to lookup a localization with. Maybe `undefined`, if the value is not i18n (app does
  not use i18n)
  @param {*} i18nValue
  a possibly internationalized value:
  - when passing a primitive value, it is returned as-is
  - when passing an object, the languageTag is used as a key within that object
  @param {*} [optionalFallback]
  a value to use if no localization is available for the given language tag
  
  @return {*}
  the localized value if found, `undefined` otherwise