Get the chart instance

I try to get the Chart instance to be able to use the `getElementAtEvent()` method. I have this :
```
onClick: (event, chartElements) => {
this.handleChartClick(event, chartElements);
}
```
And I want to access my Chart instance in my `handleChartClick`method, how can I do that ? The final purpose is to listen on click in axis labels and get their value.