code: def dir_visitor(dirname, visitor):
      
      visitor(dirname)
      for obj in os.listdir(dirname):
          obj_path = os.path.join(dirname, obj)
          if os.path.isdir(obj_path):
              dir_visitor(obj_path, visitor)
docs: _dir_visitor_
  
      walk through all files in dirname, find
      directories and call the callable on them.
  
      :param dirname: Name of directory to start visiting,
        all subdirs will be visited
      :param visitor: Callable invoked on each dir visited