anchor.diff:  class ExampleService extends Service {
     String serviceId = "example";
   
  -  ExampleService(_IsolateHandler handler) : super(handler);
  +  ExampleService(Services services, _IsolateHandler handler)
  +      : super(services, handler);
   }
   
   /**
  
positive.code: abstract class Service {
    static int _topCallId = 0;
  
    _IsolateHandler _isolateHandler;
  
    String get serviceId;
  
    Service(this._isolateHandler);
  
    String _getNewCallId() => "host_${_topCallId++}";
  
  
negative.code: 
    // Fires when the isolate communication has been established.
    Stream onReady;
    Map<String, Service> _services = {};
  
    Services() {
      _isolateHandler = new _IsolateHandler();
      registerService(new ExampleService(this, _isolateHandler));
    }
  
    Service getService(String serviceId) => _services[serviceId];
  
    void registerService(Service service) {
      _services[service.serviceId] = service;
    }
  
  }
  
  /**
  