public void canDeleteDataObject(
     DataModelerContext context,
     DataObjectTO object,
     DataModelTO model,
     ValidatorCallback callback) {
   if (!context.getHelper().isDataObjectReferenced(object.getClassName())) {
     callback.onSuccess();
   } else {
     callback.onFailure();
   }
 }
 public void canExtend(
     DataModelerContext context,
     String siblingCandidateName,
     String parentCandidateName,
     ValidatorCallback callback) {
   if (context.getHelper().isAssignableFrom(siblingCandidateName, parentCandidateName)) {
     callback.onSuccess();
   } else {
     callback.onFailure();
   }
 }