add css file located in different folder to an Asset Bundle

I have a blockui asset which load blockui js library from bower package. I want to apply a custom css file that should be included when I use BlockUI asset.

However, because blockui js lib is located in vendor/bower/blockui and my custom css is at frontend/web/css, I can not add custom css easily to blockui asset bundle and i am stucked

This is my asset bundle code





namespace frontend\assets;


use yii\web\AssetBundle;


/**

 * @author Qiang Xue <qiang.xue@gmail.com>

 * @since 2.0

 */

class BlockUIAsset extends AssetBundle

{

    public $sourcePath = '@bower';

    public $baseUrl = '@web';

    public $js = [

        'blockui/jquery.blockUI.js',

    ];


    #this does not work because it look for vendor/bower/css/custom.css which does not exist

    #my custom.css is located at frontend/web/css/

    public $css = [

        'css/custom.css'

    ];


    public $depends = [

        'yii\web\YiiAsset',

        'yii\bootstrap\BootstrapAsset',

    ];

}