docs: public static PeriodFormatter alternateExtended() {
          if (cAlternateExtended == null) {
              cAlternateExtended = new PeriodFormatterBuilder()
                  .appendLiteral("P")
                  .printZeroAlways()
                  .minimumPrintedDigits(4)
                  .appendYears()
                  .appendSeparator("-")
                  .minimumPrintedDigits(2)
                  .appendMonths()
                  .appendSeparator("-")
                  .appendDays()
                  .appendSeparatorIfFieldsAfter("T")
                  .appendHours()
                  .appendSeparator(":")
                  .appendMinutes()
                  .appendSeparator(":")
                  .appendSecondsWithOptionalMillis()
                  .toFormatter();
          }
          return cAlternateExtended;
      }