anchor.diff:  heartbeat() ->
       gen_server:cast(?MODULE, heartbeat).
   
  +force_sync() ->
  +    gen_server:call(?MODULE, force_sync).
  +
   
   %%--------------------------------------------------------------------
   %% GEN_SERVER CALLBACKS
  
positive.code: %% API
  -export([start_link/0,
           stop/0]).
  -export([heartbeat/0]).
  
  %% gen_server callbacks
  -export([init/1,
  
negative.code: 
  
  handle_call(stop,_From,State) ->
      {stop, normal, ok, State};
  
  handle_call(force_sync,_From, State) ->
      ok = sync(),
      {reply, ok, State}.
  
  
  %% Function: handle_cast(Msg, State) -> {noreply, State}          |
  