Illuminate\Database\Query\Builder::labels does not exist

I have installed package : Laravel Charts Everything done as per Docs. but when i am trying to below code in controller. laravel give me error :

        $chart = new Chart;

    $chart->labels(['One', 'Two', 'Three', 'Four']);
    $chart->dataset('My dataset', 'line', [1, 2, 3, 4]);
    $chart->dataset('My dataset 2', 'line', [4, 3, 2, 1]);

error is:

Method Illuminate\Database\Query\Builder::labels does not exist.

via Chebli Mohamed