anchor.diff:  
       handle_or_reroute(Sub, request_to_file_entry_or_provider(Sub), SessId, HandleLocally, ProvMap);
   
  -handle_cast(#subscription_cancellation{id = SubId}, #state{
  +do_handle_cast(#subscription_cancellation{id = SubId}, #state{
       event_streams = EvtStms, session_id = SessId} = State) ->
       ?debug("Removing subscription ~p from session ~p", [SubId, SessId]),
  -    {ok, EvtStm} = maps:find(SubId, EvtStms),
  -    erlang:exit(EvtStm, shutdown),
  +    case maps:find(SubId, EvtStms) of
  +        {ok, EvtStm} -> erlang:exit(EvtStm, shutdown);
  +        error -> ?warning("Cannot remove subscription ~p from session ~p: "
  +                          "subscription doesn't exist", [SubId, SessId])
  +    end,
       {noreply, State#state{event_streams = maps:remove(SubId, EvtStms)}};
   
  -handle_cast(Request, State) ->
  +do_handle_cast(Request, State) ->
       ?log_bad_request(Request),
       {noreply, State}.
   
  
positive.code: %%--------------------------------------------------------------------
  %% @private
  %% @doc
  %% Handles cast messages.
  %% @end
  %%--------------------------------------------------------------------
  -spec handle_cast(Request :: term(), State :: #state{}) ->
      {noreply, NewState :: #state{}} |
      {noreply, NewState :: #state{}, timeout() | hibernate} |
      {stop, Reason :: term(), NewState :: #state{}}.
  handle_cast({register_stream, SubId, EvtStm}, #state{event_streams = EvtStms} = State) ->
      {noreply, State#state{event_streams = maps:put(SubId, EvtStm, EvtStms)}};
  
  handle_cast({unregister_stream, SubId}, #state{event_streams = EvtStms} = State) ->
      {noreply, State#state{event_streams = maps:remove(SubId, EvtStms)}};
  
  handle_cast({flush_stream, SubId, Notify}, #state{event_streams = Stms,
      session_id = SessId} = State) ->
      case maps:find(SubId, Stms) of
          {ok, Stm} ->
  
negative.code: 
      handle_or_reroute(Evt, {provider, ProviderId}, SessId, HandleLocally, ProvMap);
  
  do_handle_cast(#subscription{id = SubId} = Sub, #state{event_stream_sup = EvtStmSup,
      session_id = SessId, event_streams = EvtStms, entry_to_provider_map = ProvMap} = State) ->
      HandleLocally =
          fun(_, NewProvMap, _) ->
  