code: public void setInto(ReadWritablePeriod duration, Object object, Chronology chrono) {
          duration.setPeriod((ReadablePeriod) object);
      }
docs: Extracts duration values from an object of this converter's type, and
  sets them into the given ReadWritablePeriod.
  
  @param duration duration to get modified
  @param object  the object to convert, must not be null
  @param chrono  the chronology to use
  @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