code: def list_files(dir_pathname,
                 recursive=True,
                 topdown=True,
                 followlinks=False):
      
      for root, dirnames, filenames\
      in walk(dir_pathname, recursive, topdown, followlinks):
          for filename in filenames:
              yield absolute_path(os.path.join(root, filename))
docs: Enlists all the files using their absolute paths within the specified
      directory, optionally recursively.
  
      :param dir_pathname:
          The directory to traverse.
      :param recursive:
          ``True`` for walking recursively through the directory tree;
          ``False`` otherwise.
      :param topdown:
          Please see the documentation for :func:`os.walk`
      :param followlinks:
          Please see the documentation for :func:`os.walk`