/**
  * @see \xml\escape() escape
  */
 public static function escapeXml($string_, Io_Charset $charset_ = null, $flags_ = ENT_QUOTES)
 {
     if (null === $charset_) {
         return \xml\escape($string_, null, ENT_XML1, $flags_);
     }
     return \xml\escape($string_, $charset_->name(), ENT_XML1, $flags_);
 }