public static String formatPath(List<ChildNumber> path){
  return PATH_JOINER.join(Iterables.concat(Collections.singleton("M"),path));
}

public static String formatPath ( List < ChildNumber > path ) { return PATH_JOINER . join ( Iterables . concat ( Collections . singleton ( "M" ) , path ) ) ; }
convert to a string path , starting with " m / "
