anchor.diff:          | Some x -> None
   
   (* ------------------------------------------------------------------------------- *)
  -let bytes_of_key (k : SessionIndex) =
  +let bytes_of_key (k : byte[] * Role * string) =
       let bf = new BinaryFormatter () in
       let m  = new MemoryStream () in
           bf.Serialize(m, k); m.ToArray ()
  
positive.code: 
  (* ------------------------------------------------------------------------------- *)
  let insert self sid role hint value =
      let key = bytes_of_key (sid,role,hint) in
      let insert (db : DB.db) =
          match DB.get db key with
          | Some _ -> ()
  
negative.code: 
  (* ------------------------------------------------------------------------------- *)
  let select self sid role hint =
      let key = bytes_of_key (Bytes.cbytes sid, role, hint) in
  
      let select (db : DB.db) =
          let filter_record ((sinfo, ts) : StorableSession * _) =
  