Stop using from A import *

[zxul767]

This is a common practice in fastai notebooks and while it is probably harmless in the context of the course, I think it's a bad practice in general due to the potential for silent shadowing of function and variable names.

We should rewrite the notebooks to use the more commonly used practice of using a very short but common prefix. pandas uses pd, numpy uses np, seaborn uses sns, etc.