code: @Override
      public void setUpdatePeriod(final String updatePeriod) {
          if (!PERIODS.contains(updatePeriod)) {
              throw new IllegalArgumentException("Invalid period [" + updatePeriod + "]");
          }
          this.updatePeriod = updatePeriod;
      }
docs: Sets the Syndication module update period.
  <p>
  
  @param updatePeriod the Syndication module update period to set, <b>null</b> if none.