anchor.diff:    int page = 0;
   
     bool _hasNext = true;
  +  bool _finishedWithError = false;
     int _version = 0;
     RestListingDriver _driver;
   
  
positive.code: 
    bool get working => rest.working;
    bool get hasNext => _hasNext;
  
    /// Use this to indicate that next page should be loaded.
    Future<bool> loadNextPage() async {
      if (working || !hasNext) {
        return false;
      }
  
negative.code:     int reqVersion = _version;
      RestResult rr = await client.get();
      if (_version != reqVersion) return false;
      if (rr.error || rr.failure) {
        _finishedWithError = true;
        _hasNext = false;
        return false;
      }
  
      UnpackedData data = _driver.unpackData(rr.data);
      page++;
  