yolo_tensorflow test.py cannot use

[gino07172002]

as the readme, type python test.py
only shows:
Traceback (most recent call last):
File "test.py", line 83, in
main()
File "test.py", line 42, in main
saver.restore(sess, tf.train.latest_checkpoint("checkpoint"))
File "C:\Users\acer\AppData\Roaming\Python\Python36\site-packages\tensorflow\p
ython\training\saver.py", line 1534, in restore
raise ValueError("Can't load save_path when it is None.")
ValueError: Can't load save_path when it is None.

what happended?