Facing an error in Chapter_17th_unittest.py #4

Chapter Link: https://github.com/Sana-Rasheed/Scripts_of_Python_Programming_Book/blob/master/Chapter_17th_unittest.py
E
ERROR: C:\Users\Nasir\AppData\Roaming\jupyter\runtime\kernel-510a6c02-c3b3-432f-b96a-42c7be9fc54d (unittest.loader._FailedTest)
AttributeError: module 'main' has no attribute 'C:\Users\Nasir\AppData\Roaming\jupyter\runtime\kernel-510a6c02-c3b3-432f-b96a-42c7be9fc54d'

Ran 1 test in 0.001s
FAILED (errors=1)
An exception has occurred, use %tb to see the full traceback.
SystemExit: True