java.lang.UnsupportedOperationException: Need to implement doAddContentChild(Object, int) for class org.eclipse.gef4.zest.fx.parts.GraphContentPart
	at org.eclipse.gef4.mvc.parts.AbstractContentPart.doAddContentChild(AbstractContentPart.java:154)
	at org.eclipse.gef4.mvc.parts.AbstractContentPart.addContentChild(AbstractContentPart.java:68)
	at org.eclipse.gef4.mvc.operations.AddContentChildOperation.execute(AddContentChildOperation.java:76)
	at org.eclipse.gef4.mvc.operations.AbstractCompositeOperation.execute(AbstractCompositeOperation.java:142)
	at org.eclipse.gef4.mvc.policies.AbstractTransactionPolicy.locallyExecuteOperation(AbstractTransactionPolicy.java:140)
	at org.eclipse.gef4.mvc.policies.ContentPolicy.addContentChild(ContentPolicy.java:72)
	at org.eclipse.gef4.mvc.policies.CreationPolicy.create(CreationPolicy.java:128)
	at org.eclipse.gef4.mvc.policies.CreationPolicy.create(CreationPolicy.java:195)
	at com.capsyx.nati.ui.editor.common.policy.CreatePaletteOnClickPolicy$$anonfun$1.apply$mcV$sp(CreatePaletteOnClickPolicy.scala:103)

class CreatePaletteOnClickPolicy extends AbstractFXOnClickPolicy {
    def click(event: MouseEvent): Unit = {
        openPalette(event, positionInScreen)
    }

    private def getViewer(): FXViewer = {
        getHost().getRoot().getViewer().asInstanceOf[FXViewer]
    }
    
    private def openPalette(event: MouseEvent, positionInScreen: Point2D): Unit = {        
        val popup = new Popup()

	popup.autoFixProperty().set(true)
	popup.autoHideProperty().set(true)
	popup.setX(event.getScreenX())
	popup.setY(event.getScreenY())

	val hb = new HBox();
	hb.setStyle("-fx-border-width: 1px; -fx-border-color: DIMGRAY; -fx-background-color: lightgray" );
		
	val first = new Button()
	first.setOnAction { actionEvent: ActionEvent =>
	    onNewPlaceClicked(actionEvent, popup)
	}
	first.setText("Place")
		
	hb.getChildren().add(first);
	hb.setEffect(new DropShadow(4, 4, 2, Color.GRAY))
	hb.setSpacing(4)
	hb.setPadding(new Insets( 4, 4, 4, 4))
	popup.getContent().addAll(hb)
	popup.show(getViewer().getScene().getWindow())
    }
    
    private def onNewPlaceClicked(event: ActionEvent, popup: Popup): Unit = {        
        val root = getHost().getRoot()
	val viewer = root.getViewer()
	    
        val contentPartModel = root.getContentPartChildren().get(0).asInstanceOf[GraphContentPart]
        val graph = contentPartModel.getContent
	    
	val node = {
	    val builder = new Node.Builder()
	    builder
	        .attr(ZestProperties.ELEMENT_CSS_ID, "A")
	        .attr(ZestProperties.ELEMENT_LABEL, "A")
	            	            
            builder.buildNode()
	}
        node.setGraph(graph)
            
	val creationPolicy = root.getAdapter(classOf[CreationPolicy[javafx.scene.Node]])
	creationPolicy.init()
        // this throws the error
        creationPolicy.create(node, contentPartModel, com.google.common.collect.HashMultimap.create())
	    
        val operation = creationPolicy.commit()
	viewer.getDomain().execute(operation)
	    
	popup.hide()
    }
}