A Simple Tutorial to Classify Images Using TensorFlow — Step by Step Guide

Following the tutorial i get an error in step 3

ERROR:tensorflow:Image directory ‘’ not found.
Traceback (most recent call last):
 File “retrain.py”, line 1326, in <module>
 tf.app.run(main=main, argv=[sys.argv[0]] + unparsed)
 File “C:\Users\Buildium02\Anaconda3\lib\site-packages\tensorflow\python\platform\app.py”, line 126, in run
 File “retrain.py”, line 989, in main
 class_count = len(image_lists.keys())
AttributeError: ‘NoneType’ object has no attribute ‘keys’

can you please help?