anchor.diff:  
   %% API
   -export([start_link/0]).
  +
  +-export([
  +  get_by_user_id/1,
  +  create/1,
  +  delete/1
  +]).
   
   %% gen_server callbacks
   -export([init/1,
  
positive.code: %%%===================================================================
  %%% Internal functions
  %%%===================================================================
  
negative.code:   {noreply, NewState :: #state{}, timeout() | hibernate} |
    {stop, Reason :: term(), Reply :: term(), NewState :: #state{}} |
    {stop, Reason :: term(), NewState :: #state{}}).
  handle_call({get, Id}, _From, State) when is_integer(Id) ->
    do_get_permissions_by_user_id(State, Id);
  handle_call({create, Permission}, _From, State) ->
    do_create_permission(State, Permission);
  handle_call({delete, Permission}, _From, State) ->
    do_delete_permission(State, Permission);
  handle_call(_Request, _From, State) ->
    {reply, ok, State}.
  
  