anchor.diff:  %% Function: start_link() -> {ok,Pid} | ignore | {error,Error}
   %% Description: Starts the server
   %%--------------------------------------------------------------------
  +-spec start_link() -> {ok,pid()} | ignore | {error, any()}.
   start_link() ->
       gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
   
  
positive.code: %% cleaning up. When it returns, the gen_server terminates with Reason.
  %% The return value is ignored.
  %%--------------------------------------------------------------------
  terminate(_Reason, _State) ->
      ok.
  
  
negative.code: %% Func: code_change(OldVsn, State, Extra) -> {ok, NewState}
  %% Description: Convert process state when code is changed
  %%--------------------------------------------------------------------
  -spec code_change(any(), #state{}, any()) -> {ok, #state{}}.
  code_change(_OldVsn, State, _Extra) ->
      {ok, State}.
  
  