anchor.diff:  
   class _Shard {
     int id;
  +  int heartbeatInterval;
     _WS ws;
     WebSocket socket;
     int sequence;
  
positive.code:             "seq": this.sequence
            });
          }
          break;
  
        case _OPCodes.invalidSession:
  
negative.code:   /// 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 {
  