code: public function validateModuleClass()
      {
          if (strpos($this->moduleClass, '\\') === false || Yii::getAlias('@' . str_replace('\\', '/', $this->moduleClass)) === false) {
              $this->addError('moduleClass', 'Module class must be properly namespaced.');
          }
          if (substr($this->moduleClass, -1, 1) == '\\') {
              $this->addError('moduleClass', 'Module class name must not be empty. Please enter a fully qualified class name. e.g. "cascade\modules\admin\Module".');
          }
      }
docs: Validates [[moduleClass]] to make sure it is a fully qualified class name.