Bug 138562 Splite extendsexcpetion to seperate sub class
The suggestion is Parent invalid Cycle extends Different type extends Not top level extends
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
int posn = listeners.indexOf( obj );
		if ( posn != -1 )
			listeners.remove( posn );
	}
	/**
	 * Removes all listeners on this element.
	 * <p>
	 * Part of: Notification system.
	 */
	public void clearListeners( )
	{
		if ( listeners != null )
			listeners.clear( );
		listeners = null;
	}
	/**
	 * Sends an event called by the notification framework. The default
	 * implementation sends the event to listeners of this one object. Derived
	 * classes override this to send it to additional associated objects
	 * depending on context. The subclass should set the event's delivery path
	 * to indicate these additional delivery routes.
	 * <p>
	 * Part of: Notification system.
	 * 
	 * @param ev
	 *            the event to send
	 */
	public void sendEvent( NotificationEvent ev )
	{
		ev.setDeliveryPath( NotificationEvent.DIRECT );