Use custom slug manipulation for sluggable field in Propel

In my situation, I need to use Turkish characters converted for url. You need to override cleanupSlugPart function:

protected static function cleanupSlugPart($slug, $replacement = '-')
{
// convert turkish chars
$str = str_replace('ı','i',$slug);
$str = str_replace('İ','I',$str);
$str = str_replace('ç','c',$str);
$str = str_replace('Ç','C',$str);
$str = str_replace('ğ','g',$str);
$str = str_replace('Ğ','G',$str);
$str = str_replace('ş','s',$str);
$str = str_replace('Ş','S',$str);
$str = str_replace('ü','u',$str);
$str = str_replace('Ü','U',$str);
$str = str_replace('ö','o',$str);
$slug = str_replace('Ö','O',$str);

// lowercase
if (function_exists('mb_strtolower')) {
$slug = mb_strtolower($slug);
} else {
$slug = strtolower($slug);
}

...