docs: public static PeriodFormatter wordBased(Locale locale) {
          PeriodFormatter pf = FORMATTERS.get(locale);
          if (pf == null) {
              DynamicWordBased dynamic = new DynamicWordBased(buildWordBased(locale));
              pf = new PeriodFormatter(dynamic, dynamic, locale, null);
              PeriodFormatter existing = FORMATTERS.putIfAbsent(locale, pf);
              if (existing != null) {
                  pf = existing;
              }
          }
          return pf;
      }