anchor.diff:  send_event(Message, From, {Topic, Subscriber}) ->
   	Subscriber ! {hot_proxy_event, From, {Topic, Message}},
   	ok.
  +
  +ensure_monitor(New, Existing) when is_pid(New) ->
  +	case lists:keyfind(New, 1, Existing) of
  +		{New, _MonRef} -> Existing;
  +		false          ->
  +			MonRef = monitor(process, New),
  +			[{New, MonRef} |Existing]
  +	end.
  
positive.code: -export([
  	init_tables/0,
  	subscribe/1,
  	send/2
  ]).
  
  
negative.code: 	{ok, #{ subscribers => [] }}.
  
  handle_call({subscribe, Topics}, {From, _}, #{ subscribers := Subs } = State) ->
  	NewSubs = ensure_monitor(From, Subs),
  	true = ets:insert(?MODULE, [{Topic, From} || Topic <- Topics]),
  	{reply, ok, State#{ subscribers :=  NewSubs }};
  handle_call({subscribe, Topics, Callback}, {From, _}, #{ subscribers := Subs } = State) ->
  	NewSubs = ensure_monitor(From, Subs),
  	true = ets:insert(?MODULE, [{Topic, From, Callback} || Topic <- Topics]),
  	{reply, ok, State#{ subscribers :=  NewSubs }};
  handle_call(_Request, _From, State) ->
  	{reply, ok, State}.
  