code: public void setWarningPeriod(final int warningPeriod) {
  		if (0 != warningPeriod && warningPeriod < MINIMUM_WARNING) {
  			throw new IllegalArgumentException("Warning period must be at least " + String.valueOf(
  					MINIMUM_WARNING));
  		}
  		if (warningPeriod != getWarningPeriod()) {
  			getOrCreateComponentModel().warningPeriod = warningPeriod;
  		}
  	}
docs: Set a pre-timeout warning to a specified number of seconds. This should be no less than the WCAG minimum of 20.
  <p>
  Setting the warning period to exactly ZERO (0) allows the warning time to be determined in the client layer.
  </p>
  
  @param warningPeriod The timeout warning will show this many seconds before the timeout as indicated by the
  timeoutPeriod.