Add .table-sm to GridView

Hi to all! What I want to do is just change the CSS style of my GridView (add .table-sm), but I can´t find where

<?= GridView::widget([

        'dataProvider' => $dataProvider,

        'columns' => [

            ['class' => 'kartik\grid\SerialColumn'],


            ['class' => 'kartik\grid\ActionColumn'],

        ],

        'export' => false

    ]); ?>

Thanks to all guys!

Would this help?

http://www.yiiframework.com/doc-2.0/yii-grid-gridview.html#$options-detail

So niceeeeeeeee! Thanks!