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