anchor.diff:  %%%===================================================================
   
   do_get_devices(State = #state{cache = Cache}) ->
  -  {reply, {ok, ets:tab2list(Cache)}, State}.+  {reply, {ok, ets:tab2list(Cache)}, State}.
  +
  +do_create_device(State = #state{cache = Cache}, DeviceModel) ->
  +  case em_storage:create_device(DeviceModel) of
  +    {ok, Device} ->
  +      case ets:insert_new(Cache, Device) of
  +        true ->
  +          {reply, {ok, Device}, State};
  +        false ->
  +          {reply, {error, <<"Error sync in devices cache">>}, State}
  +      end;
  +    Reason ->
  +      {reply, Reason, State}
  +  end.
positive.code: -spec(get() -> {ok, [Rec :: #device{}]} | {error, string()}).
  get() ->
    gen_server:call(?SERVER, {get}).
  
  %%--------------------------------------------------------------------
  %% @doc
  
negative.code:   {stop, Reason :: term(), NewState :: #state{}}).
  handle_call({get}, _From, State) ->
    do_get_devices(State);
  handle_call({create, User}, _From, State) ->
    do_create_device(State, User);
  handle_call(_Request, _From, State) ->
    {reply, ok, State}.
  
  