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