public Language getOrDetectLanguage(String languageDetectionText) {
        if (language != null  && language != Language.UNKNOWN) return language;
        if (model.isPresent()) return model.get().getParsingLanguage(languageDetectionText);
        return Language.UNKNOWN; // against the promise in the JavaDoc, but it is not locally ensured
    }
Returns the language to use when parsing, with a text to use for detection if necessary.
if not decided by the item under parsing. This is never null or UNKNOWN
container-search/src/main/java/com/yahoo/search/query/parser/Parsable.java