anchor.diff:  notify(_Msg, S = #state{}) ->
       %% unexpected
       {next_state, notify, S}.
  +
  +notify({enqueue, Msg}, From, S = #state{}) ->
  +    gen_fsm:reply(From, ok),
  +    send_notification(insert(Msg, S)).
   
   %% @private
   handle_event(_Event, StateName, State) ->
  
positive.code:     %% unexpected
      {next_state, active, S}.
  
  %% @private
  passive(notify, #state{size=0} = S) ->
      {next_state, notify, S};
  
negative.code: %% @doc Enqueues a message.
  -spec enqueue(pid(), term()) -> ok.
  enqueue(Queue, Msg) ->
      case catch gen_fsm:sync_send_event(Queue, {enqueue, Msg}, infinity) of
          ok -> ok;
          {'EXIT', _Reason} ->
              % we are not allowed to crash, this would
              % teardown 'decoupled' publisher process
              ok
      end.
  
  
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  %%% gen_fsm Function Definitions %%%
  