anchor.diff:  -spec(get() -> {ok, [Rec :: #device{}]} | {error, string()}).
   get() ->
     gen_server:call(?SERVER, {get}).
  +
  +-spec(create(Device :: #device{}) -> {ok, #device{}} | {error, string()}).
  +create(Device) ->
  +  gen_server:call(?SERVER, {create, Device}).
   
   %%--------------------------------------------------------------------
   %% @doc
  
positive.code: %%%===================================================================
  
  do_get_devices(State = #state{cache = Cache}) ->
    {reply, {ok, ets:tab2list(Cache)}, State}.
negative.code: -export([start_link/0]).
  
  -export([
    get/0,
    create/1
  ]).
  
  %% gen_server callbacks
  