message: Clarify tf.io.gfile.walk docstring.
diff: @@ -656,9 +656,9 @@ def walk(top, in_order=True):
  Yields:
  Each yield is a 3-tuple: the pathname of a directory, followed by lists of
  - all its subdirectories and leaf files.
  - (dirname, [subdirname, subdirname, ...], [filename, filename, ...])
  - as strings
  + all its subdirectories and leaf files. That is, each yield looks like:
  + `(dirname, [subdirname, subdirname, ...], [filename, filename, ...])`.
  + Each item is a string.
  """
  return walk_v2(top, in_order)
  @@ -676,9 +676,9 @@ def walk_v2(top, topdown=True, onerror=None):
  Yields:
  Each yield is a 3-tuple: the pathname of a directory, followed by lists of
  - all its subdirectories and leaf files.
  - (dirname, [subdirname, subdirname, ...], [filename, filename, ...])
  - as strings
  + all its subdirectories and leaf files. That is, each yield looks like:
  + `(dirname, [subdirname, subdirname, ...], [filename, filename, ...])`.
  + Each item is a string.
  """
  top = compat.as_str_any(top)
  try:
  