Very small nitpick:
The code under Writing addon code reads like they are kept in the same file despite being taught as if they have their own files. I suggest adding import commands/comments to better align the code's implied structure to the tutorial.
Very small nitpick:
The code under Writing addon code reads like they are kept in the same file despite being taught as if they have their own files. I suggest adding import commands/comments to better align the code's implied structure to the tutorial.