Advanced contextual alternates

Hi there,
I am making a script font and trying to get the “contextual alternates” to work. I am new to font making and not familiar with the code. I followed this tutorial:
but get stuck at this point: “Cycling through glyph classes” .

According to the tutorial I should put in these classes:

ALT1: A.ss01 B.ss01
ALT2: A.ss02 B.ss02

When I did so and then hit “compile” button I get an syntax error message. I am not sure I put the code in correct. Should there be any more code than simply A.ss01 B.ss01 in ALT 1 class?

Trying to learn, but code is all new to me, so deeply thankful for all help.

Thanx for a great font program!

How did you create the classes?

There must not be a space in the class name. And the content should just be the glyph names, separated by spaces.

Thanks for your reply! There was a space in the class name. I didn’t realise this was a rule.
It is now working. Big thanks!