anchor.diff:    {stop, Reason :: term(), NewState :: #state{}}).
   handle_call({get}, _From, State) ->
     do_get_devices(State);
  +handle_call({get, UniqueId}, _From, State) ->
  +  do_get_device_by_uid(State, UniqueId);
   handle_call({create, Device}, _From, State) ->
     do_create_device(State, Device);
   handle_call({update, Device}, _From, State) ->
  
positive.code: 
  do_get_devices(State = #state{cache = Cache}) ->
    {reply, {ok, ets:tab2list(Cache)}, State}.
  
  do_create_device(State = #state{cache = Cache}, DeviceModel) ->
    case em_storage:create_device(DeviceModel) of
  
negative.code: 
  -export([
    get/0,
    get_by_uid/1,
    create/1,
    update/1,
    delete/1
  