anchor.diff:  
   %% @doc writes the value of a key
   %% @spec write(key(), value()) -> ok | {fail, term()}
  +-spec write(key(), value()) -> ok | {fail, term()}.
   write(Key, Value) ->
       case util:tc(transaction_api, single_write, [Key, Value]) of
           {_Time, commit} ->
  
positive.code: %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  
  %% @type key() = term(). Key
  %% @type value() = term(). Value
  
  process_request_list(TLog, ReqList) ->
      erlang:put(instance_id, process_dictionary:find_group(cs_node)),
  
negative.code:                                        Result2 == ok ->
                                             {{ok, done}, TransLog2};
                                         true ->
                                             {{fail, write}, TransLog2}
                                     end;
                                 true ->
                                     {{fail, {key_changed, ReadValue}}, TransLog1}
  