anchor.diff:  abstract class Service {
     static int _topCallId = 0;
   
  +  Services _services;
     _IsolateHandler _isolateHandler;
   
     String get serviceId;
   
  -  Service(this._isolateHandler);
  +  Service(this._services, this._isolateHandler);
   
     String _getNewCallId() => "host_${_topCallId++}";
   
  
positive.code: class ExampleService extends Service {
    String serviceId = "example";
  
    ExampleService(_IsolateHandler handler) : super(handler);
  }
  
  /**
  
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;
    }
  
  }
  
  /**
  