Yii2 - using kartik Select2 as filter input of GridView

'filter' => Select2::widget([
    'name' => 'CampaignSearch[partner_id]',
    'model' => $searchModel,
    'value' => $searchModel->partner_id,
    'data' => ArrayHelper::map(
        Partner::getAll(), 'id', 'name'
    ),
    'size' => Select2::MEDIUM,
    'options' => [
        'placeholder' => '-- Tất cả --',
        'style' => 'width: 300px;'
    ],
    'pluginOptions' => [
        'allowClear' => true
    ],
    'addon' => [
        'prepend' => [
            'content' => '<i class="glyphicon glyphicon-folder-open"></i>'
        ]
    ],
]),