guile-examples/json/guix-env/manifest.scm

(specifications->manifest
 ;; actually the version infos are redundant as the channels
 ;; are specified in channels.scm. however, if anyone uses
 ;; the manifest without channels, then version infos might
 ;; be relevant.
 '("guile@3.0.4"
   "guile-json@4.3.2"))