tf.gfile.Walk( top, in_order=True )
Recursive directory tree generator for directories.
top: string, a Directory name
in_order: bool, Traverse in order if True, post order if False.
Errors that happen while listing directories are ignored.
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