This code segment works for the presenter, Huw, at https://youtu.be/8ibI5bfssCU?list=PLZHx5heVfgEvuveKG1T7BBSuDOTHl1eLl&t=1481

but it fails for me.

The Screen grab shows my code and error on left and working code on right.

What am I missing? Please be gentle ;-)