code: @Override
  	public void start(Geometry geometry) {
  		if (started) {
  			return;
  		}
  		this.geometry = geometry;
  		if (geometry == null) {
  			throw new IllegalArgumentException("Null geometry not allowed.");
  		}
  		started = true;
  		eventBus.fireEvent(new GeometryEditStartEvent(geometry));
  	}
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