code: public YearMonth minusMonths(long monthsToSubtract) {
          return (monthsToSubtract == Long.MIN_VALUE ? plusMonths(Long.MAX_VALUE).plusMonths(1) : plusMonths(-monthsToSubtract));
      }
docs: Returns a copy of this {@code YearMonth} with the specified number of months subtracted.
  <p>
  This instance is immutable and unaffected by this method call.
  
  @param monthsToSubtract  the months to subtract, may be negative
  @return a {@code YearMonth} based on this year-month with the months subtracted, not null
  @throws DateTimeException if the result exceeds the supported range