code: public R setUnsharedAt(Date unsharedAt) throws ParseException {
          JsonObject jsonObject = getSharedLinkJsonObject();
          if (unsharedAt == null){
              jsonObject.add(BoxSharedLink.FIELD_UNSHARED_AT, JsonValue.NULL);
          } else {
              jsonObject.add(BoxSharedLink.FIELD_UNSHARED_AT, BoxDateFormat.format(unsharedAt));
          }
          BoxSharedLink sharedLink = new BoxSharedLink(jsonObject);
          mBodyMap.put(BoxItem.FIELD_SHARED_LINK, sharedLink);
          return (R) this;
      }
docs: Sets the date that this shared link will be deactivated. If this is set to null it will remove the
  unshared at date that is set on this item.
  Note: the date will be rounded to the day as the API does not support hours, minutes, or seconds
  
  @param unsharedAt the date that this shared link will be deactivated.
  @return  the updated request
  @throws ParseException thrown if date provided cannot be properly parsed.