Unfortunately things move fast around here.
The basic problem is probably that you’ve copied the code in the guide, rather than following the instructions.
This is a compare of the code you just shared with the current source code:
ie very different! (and therefore likely to break!)
What you need to do (as per the instructions) is go to the source code and copy the current code and change that to suit your needs.
In other words, the code in the guide is out of date, if not the instructions, which are still valid.