public static final function fcm(string $string, string $separator = '_'): string {
		return ltrim(preg_replace_callback('/\\\?[A-Z][A-Za-z0-9]+?/', function($Macthes) use ($separator){
			return $separator . ltrim(strtolower($Macthes[0]), '\\');
		}, $string), $separator);
	}