'NoneType' object has no attribute 'copy'

[TangoTime25]

So I am trying to run the entire code using my own fingerprint dataset, however, I have been getting an error which I am not too sure how to debug. It is related to the Normalization.py and the fingerprint_pipeline.py file. The error I am getting is 'NoneType' object has no attribute 'copy'. This was the error message from the terminal. Could someone give me a hint on what i can do to debug please. Many thanks.
File "fingerprint_pipeline.py", line 69, in
results = fingerprint_pipline(img)
File "fingerprint_pipeline.py", line 19, in fingerprint_pipline
norm_img = normalize(input_img.copy(), float(100), float(100))
AttributeError: 'NoneType' object has no attribute 'copy'