anchor.diff:  
   -spec get_user_info(UserId :: binary() ) -> {ok, UserInfo :: map()} | {error, term()}.
   get_user_info(UserId) ->
  -    lookup_user(UserId).
  +    retrieve_user_info(UserId).
   
   %% gen_server.
   
  
positive.code: 	{ok, #state{}}.
  
  handle_call({insert,UserInfo}, _From, State) ->
      Result = atomic_insert_new_user(UserInfo),
      {reply, Result, State};
  handle_call(_Request, _From, State) ->
  	{reply, ignored, State}.
  
negative.code:     insert_user(UserInfo).
  
  insert_user({ok, UserInfo}) ->
      {ok, UserId} = gen_server:call(?MODULE,{insert,UserInfo}),
      {ok, UserId};
  insert_user({error, not_found}) ->
      {error, not_found}.
  
  
  
  sync_insert_new_user(UserInfo) ->
      UserIdList = maps:get(user_ids,UserInfo,[]),
      UserId = maps:get(uid, UserInfo),
      case add_new_user_entries(UserIdList,UserId,UserInfo) of
          ok -> 
              {ok, UserId};
  