@Override
 public boolean relationshipIsDeleted(long relationshipId) {
   if (primitiveElement == null) {
     return false;
   }
   CowRelElement relationshipElement = primitiveElement.relationshipElement(relationshipId, false);
   return relationshipElement != null && relationshipElement.isDeleted();
 }
 @Override
 public void deleteRelationship(long id) {
   PrimitiveElement element = getPrimitiveElement(true);
   element.relationshipElement(id, true).setDeleted();
 }