The issue I find with this pattern in docs/tutorials is that the prefix makes it very obvious which functions are from this library.

It's particularly worthwhile when looking at the bigger examples that might involve another library, or stdlib functions/libs I haven't dealt with before

To each his own. Some drawbacks here are that it means that if you want to copy the code in, you have to add all the “p9”s. And, if you want to make a more complicated demo, with maybe a second import, you now have multiple conventions in your demo codebase.