anchor.diff:  -spec set_filter_predicate(pid(), escalus_connection:filter_pred()) -> ok.
   set_filter_predicate(Pid, Pred) ->
       gen_server:call(Pid, {set_filter_pred, Pred}).
  +
  +-spec get_tls_last_message(pid()) -> {ok, binary()} | {error, undefined_tls_message}.
  +get_tls_last_message(Pid) ->
  +    gen_server:call(Pid, get_tls_last_message).
   
   -spec stop(pid()) -> ok | already_stopped.
   stop(Pid) ->
  
positive.code:          stream_start_req/1,
           stream_end_req/1,
           assert_stream_start/2,
           assert_stream_end/2]).
  
  %% gen_server callbacks
  -export([init/1,
  
negative.code:     {reply, ok, set_active_opt(State,Active)};
  handle_call({set_filter_pred, Pred}, _From, State) ->
      {reply, ok, State#state{filter_pred = Pred}};
  handle_call(get_tls_last_message, _From,
              #state{socket = Socket, ssl = true, tls_module = fast_tls} = S) ->
      Reply = {ok, fast_tls:get_tls_last_message(self, Socket)},
      {reply, Reply, S};
  handle_call(get_tls_last_message, _From, #state{} = S) ->
      {reply, {error, undefined_tls_message}, S};
  handle_call(kill_connection, _, #state{socket = Socket, ssl = SSL, tls_module = TLSMod} = S) ->
      case SSL of
          true -> TLSMod:close(Socket);
  