How to unlink a relation in the entity model?

Hi,

I the entity management model in vRO I can "link" a child entity to its parent, however I can't get the "unlink" to work.

For example: if I want to link a VM to a parent VM object, I do:

:
:
// Attach the parentEntity
var updateLinks = new Properties;
updateLinks.put('ParentVirtualMachine', parentEntity);

var vcacEntity = System.getModule("com.vmware.library.vcac").updateVCACEntity(nodeEntity.hostId, nodeEntity.modelName, nodeEntity.entitySetName, nodeEntity.keyString, nodeProperties, updateLinks, headers);

and v.v. for the "unlink" action:

:
:
// Detach the parent
var updateLinks = new Properties;
updateLinks.put('ParentVirtualMachine', null);


var vcacEntity = System.getModule("com.vmware.library.vcac").updateVCACEntity(nodeEntity.hostId, nodeEntity.modelName, nodeEntity.entitySetName, nodeEntity.keyString, nodeProperties, updateLinks, headers);

I am using LINQPad so I can see the results of each test. The "link" as shown above does populate the releationships (ParentVirtualMachine, ChildVirtualMachines), but the "unlink" does not seem to have any effect?

Tx,

Ed