anchor.diff:  -module(device_directory).
   -behaviour(gen_server).
   
  +-compile({parse_transform, lager_transform}).
  +
   %% API.
   -export([start_link/0]).
  +-export([list_devices/1]).
   
   %% gen_server.
   -export([init/1]).
  
positive.code: start_link() ->
    gen_server:start_link(?MODULE, [], []).
  
  %% gen_server.
  
  init([]) ->
    {ok, #state{}}.
  
  handle_call(_Request, _From, State) ->
    {reply, ignored, State}.
  
  handle_cast(_Msg, State) ->
    {noreply, State}.
  
  handle_info(_Info, State) ->
    {noreply, State}.
  
  
negative.code: -export([terminate/2]).
  -export([code_change/3]).
  
  -record(state, {devices}).
  
  %% API.
  