class not found error in SweetAlert package yii2

I am new in yii2. i have install SweetAlert using following command

composer require light/yii2-widget-sweet-alert=dev-master

And in my _form.php

use light\widgets\SweetAlert;


    'title' => 'Hii',

    'text' => 'Are you sure'


But it gives me following error

Class 'light\widgets\SweetAlert' not found

I follow all step given in its document.

What is wrong?

Are you sure that your composer added SweetAlert library in vendor?

Please check it is installed or not. If yes then Please check your configuration whether vendor library configured correctly or not.