ElementDefs for lots of elements contain references to external code lists. What is a proper way to utilize those links? For example:

E1271 = t::AN.new(:E1271, "Industry Code"                        , 1, 30,
            s::CodeList.external("508"))

Inspecting an AN referencing an external list just calls a #to_s on CodeList::External. I've found a note in todo with the following content:

"Support for configurable external code sources. The minimal interface should
implement #include?(code). Need to decide how to handle unconfigured external
code sources -- should there be a method to list all the code sources in some
transaction set?"

This is dated 2011, so i believe it has never been implemented since. I would like to either figure out on how to make those external code lists of use in case i missed something, or collect opinions on what you think the best way to implement this with minimal impact in case it's still a pending milestone.