anchor.diff:                      return geometry,Unchecked.defaultof<_>
                   }
   
  -            let undoLoad (geo,ref) = Log.line "rollback, undo load data"
  +            let undoLoad (geo,ref) = () //Log.line "rollback, undo load data"
   
               let addToPool (ig,r) =
                   async {
  
positive.code:                 }
  
              let removeFromPool (ig,r) = 
                  Log.line "rollback, remove from pool."; 
                  pool.Remove ig |> ignore
  
              let addToRender (ig,r) =
  
negative.code:             let cts = new System.Threading.CancellationTokenSource()
              let result = ref Unchecked.defaultof<_>
              let r = geometriesNew.GetOrAdd(n, (cts, result))
              try
                  Async.RunSynchronously(LoadIntoPool.runWithCompensations result effects, cancellationToken= cts.Token)
              with | :? OperationCanceledException as o -> ()
              r
                      
          member x.Remove(n : LodDataNode) =
  