anchor.diff:    /// Sends a heartbeat packet.
     void heartbeat() {
       this.send("HEARTBEAT", this.sequence);
  +    new Timer(heartbeatInterval, (Timer t) => heartbeat());
     }
   
     Future<Null> handleMsg(String msg, bool resume) async {
  
positive.code:             "seq": this.sequence
            });
          }
          break;
  
        case _OPCodes.invalidSession:
  
negative.code: 
  class _Shard {
    int id;
    int heartbeatInterval;
    _WS ws;
    WebSocket socket;
    int sequence;
  