SAP Cloud SDK : Enhance the Registered Product TI screen Issue

Hi Experts,

I have small requirement

1) Enhance the standard business object and add some extensions fields.

2) Add those extension fields under the port binding to use in mashups parameters bindings.

     2.1) How its possible using SDK or KUT?

When i enhance the Registered Product using

Select Namespace : "AP.FO.ProductBusinessPartnerRelationManagement.Global"

And Select BO : 'ProductBusinessPartnerRelation".

And Add some extension fields i am getting error while save or activate the XBO as shown below.

Anyone have idea why its give this error for this Standard business object

" Node 'Root' of business object 'ProductBusinessPartnerRelation' is not extendable."

Many Thanks,

Mithun