Missing Class in Custom Language Support Tutorial Part2

I am currently using the Custom Language Support Tutorial (1) for my project.

It may be me own fault, but in the sixth topic classes, named as "SimpleProperty" and "SimpleElementFactory" are referenced. But there is not a single letter about how to create those classes in case they are not auto-generated and I overlooked the part how to generate them and what to put in there.

I hope you are capable of helping me out on this one!

 

Best regards,

Fuchs

 

 

(1): https://www.jetbrains.org/intellij/sdk/docs/tutorials/custom_language_support_tutorial.html