Chord semantics patch make errors

[Winston, Charles R.]

Hi developers,

First, happy new year!

A patch of mine is currently under review. When running make doc, I’m getting 
some warnings, although when run lilypond on the same files that give the 
warnings, everything works perfectly fine. The main error that is happening is:

warning: cannot find property type-check for ‘chord-semantics’ (music-type?). 
perhaps a typing error?

I believe that this is coming from line 97 of lily/chord-name-engraver.cc in my 
patch. I say

semantics = chord_semantics_event_->get_property (“chord-semantics”)

This property of the chord semantics event chord-semantics is supposed to be a 
scheme alist representing the semantics of the chord. I guess I’m not defining 
this property correctly. But it’s puzzling to me that this still works when 
running the files, giving no warnings. Would anyone know why this would happen?

Here’s the link to the patch:
https://codereview.appspot.com/337870043