Saves checkpoints every N steps or seconds.

Inherits From: SessionRunHook

checkpoint_dir str, base directory for the checkpoint files.
save_secs int, save every N secs.
save_steps int, save every N steps.
saver Saver object, used for saving.
checkpoint_basename str, base name for the checkpoint files.
scaffold Scaffold, use to get saver object.
listeners List of CheckpointSaverListener subclass instances. Used for callbacks that run immediately before or after this hook saves the checkpoint.
save_graph_def Whether to sa