An input function, typically generated by the input_fn() helper function.

A list of R functions, to be used as callbacks inside the training loop. By default, hook_history_saver(every_n_step = 10) and hook_progress_bar() will be attached if not provided to save the metrics history and create the progress bar.

The path to a specific model checkpoint to be used for prediction. If NULL (the default), the latest checkpoint in model_dir is used.