code: public Attributes withExpires(DateTime expires) {
          if (expires == null) {
              this.expires = null;
          } else {
              this.expires = expires.toDateTime(DateTimeZone.UTC).getMillis() / 1000;
          }
          return this;
      }
docs: Set the expires value.
  
  @param expires the expires value to set
  @return the Attributes object itself.