ThemeModule.php

<?php
namespace app\web\theme\module;

use Yii;
use yii\base\Module;
use yii\base\BootstrapInterface;

/**
 * Class ThemeModule is the Module class for your Theme and site-specific functions
 * @package app\web\theme\module
 */
class ThemeModule extends Module implements BootstrapInterface
{
    /**
     * @inheritdoc
     */
    public function bootstrap($app)
    {
        Yii::$classMap['app\models\Slide'] = '@webroot/theme/module/models/Slide.php';
    }
}