ly:context-mod? list to string

[Urs Liska]

When I use ly:context-mod? for a parameter in a music function a string 
as the final part will be cut to list items.

if I write
\function \with { comment = "This should be verified" }

then the ly:context-mod? variable will hold

((assign comment This should be verified))

cdr-ing makes it (comment This should be verified)

So what's the best (or canonic) way to make that (comment "This should 
be verified") again?

TIA
Urs