code: @Override
      public ChronoZonedDateTime<D> plus(long amountToAdd, TemporalUnit unit) {
          if (unit instanceof ChronoUnit) {
              return with(dateTime.plus(amountToAdd, unit));
          }
          return ChronoZonedDateTimeImpl.ensureValid(getChronology(), unit.addTo(this, amountToAdd));   /// TODO: Generics replacement Risk!
      }
docs: -----------------------------------------------------------------------