Legend selection gets reset after auto refresh

I've implement the c3/js graphs in my meanJS application it works well but i've added functionality where created graphs will auto refresh after specific amount refresh interval time issue is with legend selection
Legend selection gets reset graph after auto refresh how to solve this issue

```

setInterval(() => {
this.levelsData[index] = graphDetail.levels[0];
this.getGraphData(0, graphDetail, graphDetail.levels[0], index);
}, graphDetail.refreshInterval*1000);
```

* **C3 version**: 0.4.15
* **D3 version**:
* **Browser**: Chrome Version 63.0.3239.132
* **OS**: Linux