[luatex] Documentation about fonts.handlers.otf.addfeature, etc.

[Mingranina Gingranina]

 Dear List,
 Hello,

 Sorry if this isn't the right place to post this, but wasn't sure.
The following commands are used in some of the examples of Lua(La)TeX
on the net:

 fonts.handlers.otf.addfeature, fonts.protrusions.vectors,
fonts.expansions.classes, etc.

 I searched too much to find some kind of documentation about them but
I couldn't find anything

 Are there any documentation about these commands?

 Any help would be gratefully appreciated.

 Thanks,
 Mingranina