code: public function assets($data = null, $secure = false)
      {
          $data = (! is_null($data))
              ? $this->url . '/' . ASSETS_FOLDER . '/' . $data
              : $this->url . '/' . ASSETS_FOLDER . '/';
          return $this->getUrl($data, $secure);
      }
docs: Get assets directory for app.
  
  @param string $data
  @param bool   $secure
  
  @return string