Kirki_Helper::init_filesystem PHP Method

        public static function init_filesystem()
        {
            global $wp_filesystem;
            if (empty($wp_filesystem)) {
                require_once ABSPATH . '/wp-admin/includes/file.php';
                WP_Filesystem();
            }
        }

 public function include_stylesheets()
 {
     $config = apply_filters('kirki/config', array());
     $styles = '';
     Kirki_Helper::init_filesystem();
     global $wp_filesystem;
     /**
      * Include the width CSS if necessary
      */
     if (isset($config['width'])) {
         $styles .= $wp_filesystem->get_contents(Kirki::$path . DIRECTORY_SEPARATOR . 'assets' . DIRECTORY_SEPARATOR . 'css' . DIRECTORY_SEPARATOR . 'customizer-dynamic-css-width.css');
         /**
          * Replace width placeholder with actual value
          */
         $styles = str_replace('WIDTH', $config['width'], $styles);
     }
     /**
      * Include the color modifications CSS if necessary
      */
     if (false !== $this->color_back && false !== $this->color_font) {
         $styles .= $wp_filesystem->get_contents(Kirki::$path . DIRECTORY_SEPARATOR . 'assets' . DIRECTORY_SEPARATOR . 'css' . DIRECTORY_SEPARATOR . 'customizer-dynamic-css-colors.css');
     }
     /**
      * Include generic CSS for controls
      */
     $styles .= $wp_filesystem->get_contents(Kirki::$path . DIRECTORY_SEPARATOR . 'assets' . DIRECTORY_SEPARATOR . 'css' . DIRECTORY_SEPARATOR . 'customizer-dynamic-css.css');
     return $styles;
 }