anchor.diff:           experiment_started/0,
            convergence/0,
            batch/3,
  +         event/1,
            stop/0,
            log_files/0]).
   
  
positive.code:     record_batch(Start, End, Events),
      {reply, ok, State};
  
  handle_call(experiment_started, _From, #state{}=State) ->
      record_experiment_started(),
      {reply, ok, State};
  
negative.code: -spec batch(term(), term(), number()) -> ok | error().
  batch(Start, End, Events) ->
      gen_server:call(?MODULE, {batch, Start, End, Events}, infinity).
  
  -spec event(term()) -> ok | error().
  event(Duration) ->
      gen_server:call(?MODULE, {event, Duration}, infinity).
  
  -spec experiment_started() -> ok | error().
  experiment_started() ->
  