public function getAssetManager()
    {
        if (!is_object($this->_assetManager)) {
            $options = $this->_assetManager;
            if (empty($options['__class'])) {
                $options['__class'] = AssetManager::class;
            }
            if (!isset($options['basePath'])) {
                throw new Exception("Please specify 'basePath' for the 'assetManager' option.");
            }
            if (!isset($options['baseUrl'])) {
                throw new Exception("Please specify 'baseUrl' for the 'assetManager' option.");
            }

            if (!isset($options['forceCopy'])) {
                $options['forceCopy'] = true;
            }

            $this->_assetManager = $this->app->createObject($options);
        }

        return $this->_assetManager;
    }