echo $form->field($model, 'list')->widget(
    'kolyunya\yii2\widgets\bootstrap\CheckboxList',
    [
        'items' =>
        [
            'value-1' => 'label-1',
            'value-2' => 'label-2',
            'value-3' => 'label-3'
        ],
        'type' => 'primary',
        'size' => 'default'
    ]
);