message: checkpoint_management.py - add short description for checkpoint_name parameter in the doc string
diff: @@ -533,6 +533,7 @@ class CheckpointManager(object):
  checkpoint will be preserved if it has been at least
  `keep_checkpoint_every_n_hours` since the last preserved checkpoint. The
  default setting of `None` does not preserve any checkpoints in this way.
  + checkpoint_name: Custom name for the checkpoint file.
  Raises:
  ValueError: If `max_to_keep` is not a positive integer.
  