code: public CalendarWeek minus(Weeks weeks) {
  
          if (weeks.isEmpty()) {
              return this;
          }
  
          PlainDate date = this.start.getTemporal().minus(weeks.getAmount(), CalendarUnit.WEEKS);
          int y = date.getInt(YEAR_OF_WEEKDATE);
          int w = date.getInt(WEEK_OF_YEAR);
          return CalendarWeek.of(y, w);
  
      }
docs: /*[deutsch]
  <p>Subtrahiert die angegebenen Wochen von dieser Kalenderwoche. </p>
  
  @param   weeks       the count of weeks to be subtracted
  @return  result of subtraction