code: public void setDefaultAlertThreshold(AlertThreshold alertThreshold) {
  		if (alertThreshold == null || alertThreshold == AlertThreshold.DEFAULT) {
  			throw new IllegalArgumentException("Parameter alertThreshold must not be null or DEFAULT.");
  		}
  		this.defaultAlertThreshold = alertThreshold;
  	}
docs: Sets the alert threshold that should be returned when set to {@link AlertThreshold#DEFAULT}.
  
  @param alertThreshold the value of default alert threshold.
  @throws IllegalArgumentException if the given parameter is {@code null} or {@code AlertThreshold.DEFAULT}.
  @since 2.7.0
  @see #setDefaultAlertThreshold(AlertThreshold)
  @see #setAlertThreshold(AlertThreshold)