anchor.diff:  
   %% API.
   -export([start_link/0]).
  -
   -export([get_user/2]).
  --export([remove_user_by_pid/1]).
  +-export([user_shutting_down/1]).
   
   %% gen_server.
   -export([init/1]).
  
positive.code: lookup_user(ID) ->
     tts_data:user_get_pid(ID). 
  
  %% set_pid_for_id(ID,Pid) ->
  %%    tts_data:user_update_pid(ID,Pid). 
  
  delete_user_pid(Pid) ->
      tts_data:user_delete_pid(Pid),
      ok.
  
negative.code: 
  -spec get_user(UserSuject :: binary(), Issuer :: binary()) -> {ok, pid()} | {error, term()}.
  get_user(UserSubject, Issuer) ->
      load_or_return_user(#{ sub => UserSubject, iss => Issuer}).
  
  -spec user_shutting_down(ID :: binary()) -> ok.
  user_shutting_down(ID) ->
      gen_server:call(?MODULE,{delete_user,ID}).
  
  %% gen_server.
  
  init([]) ->
  	{ok, #state{}}.
  
  handle_call({create,UserId}, _From, State) ->
      Result = create_new_user(UserId),
      {reply, Result, State};
  handle_call({delet_user,ID}, _From, State) ->
      delete_user(ID),
      {reply, ok, State};
  handle_call(_Request, _From, State) ->
  	{reply, ignored, State}.
  