docs: public MoneyFormatterBuilder appendSigned(
              MoneyFormatter whenPositive, MoneyFormatter whenZero, MoneyFormatter whenNegative) {
          MoneyFormatter.checkNotNull(whenPositive, "MoneyFormatter whenPositive must not be null");
          MoneyFormatter.checkNotNull(whenZero, "MoneyFormatter whenZero must not be null");
          MoneyFormatter.checkNotNull(whenNegative, "MoneyFormatter whenNegative must not be null");
          SignedPrinterParser pp = new SignedPrinterParser(whenPositive, whenZero, whenNegative);
          return appendInternal(pp, pp);
      }