anchor.diff:  
       %% Write trace.
       lists:foreach(fun(Line) ->
  -        io:format(File, "~p", [Line])
  +        io:format(CurrentTraceFile, "~p", [Line])
           end, Trace),
   
       {reply, ok, State};
  
positive.code: handle_call({identify, Identifier}, _From, State) ->
      lager:info("~p: identifying trace: ~p", [?MODULE, Identifier]),
      {reply, ok, State#state{identifier=Identifier}};
  handle_call(print, _From, #state{trace=Trace, file=File}=State) ->
      lager:info("~p: printing trace", [?MODULE]),
  
      lists:foldl(fun({Type, Message}, Count) ->
  
negative.code: 
      %% Open trace file for writing.
      case file:open("/tmp/partisan.trace", [write]) of
          {ok, CurrentTraceFile} ->
              {ok, #state{trace=[], current_trace_file=CurrentTraceFile}};
          {error, Error} ->
              lager:error("couldn't open trace file for writing."),
              {stop, Error}
  