code: @Nonnull
    @ReturnsMutableCopy
    public static ICommonsMap <Locale, String> getAllLocaleDisplayNames (@Nonnull final Locale aContentLocale)
    {
      ValueEnforcer.notNull (aContentLocale, "ContentLocale");
  
      return new CommonsHashMap <> (LocaleCache.getInstance ().getAllLocales (),
                                    Function.identity (),
                                    aLocale -> getLocaleDisplayName (aLocale, aContentLocale));
    }
docs: Get all possible locale names in the passed locale
  
  @param aContentLocale
  the locale ID in which the language list is required
  @return The mapping from the input locale to the display text. The result
  map is not ordered.