Setup directories.

def setup_directories(base_dir, subdirs):
  """Setup directories."""
  base_dir = os.path.expanduser(base_dir)
  tf.gfile.MakeDirs(base_dir)

  all_dirs = {}
  for subdir in subdirs:
    if isinstance(subdir, six.string_types):
      subdir_tuple = (subdir,)
    else:
      subdir_tuple = subdir
    dir_name = os.path.join(base_dir, *subdir_tuple)
    tf.gfile.MakeDirs(dir_name)
    all_dirs[subdir] = dir_name
  return all_dirs