code: public void unlinkFK(Object targetObject, ClassDescriptor cld, ObjectReferenceDescriptor rds)
      {
          setFKField(targetObject, cld, rds, null);
      }
docs: Unkink FK fields of target object.
  
  @param targetObject real (non-proxy) target object
  @param cld {@link ClassDescriptor} of the real target object
  @param rds An {@link ObjectReferenceDescriptor} or {@link CollectionDescriptor}
  associated with the real object.