code: public void setInto(ReadWritablePeriod writablePeriod, Object object, Chronology chrono) {
          ReadableDuration dur = (ReadableDuration) object;
          chrono = DateTimeUtils.getChronology(chrono);
          long duration = dur.getMillis();
          int[] values = chrono.get(writablePeriod, duration);
          for (int i = 0; i < values.length; i++) {
              writablePeriod.setValue(i, values[i]);
          }
      }
docs: Extracts duration values from an object of this converter's type, and
  sets them into the given ReadWritableDuration.
  
  @param writablePeriod  period to get modified
  @param object  the object to convert, must not be null
  @param chrono  the chronology to use, must not be null
  @throws NullPointerException if the duration or object is null
  @throws ClassCastException if the object is an invalid type
  @throws IllegalArgumentException if the object is invalid