public static String getMacroLanguage(String languageTag) {
        // TODO make it so
        return languageTag;
    }
If language is a specific variant of a macro language (e.g. 'nb' for Norwegian Bokmal),
return the macro language (e.g. 'no' for Norwegian). If it doesn't have a macro language,
return unchanged.

@param languageTag
@return
tika-core/src/main/java/org/apache/tika/language/detect/LanguageNames.java