Comment #12 on issue 2872 by [email protected]: Patch: Provide define-session and define-session-public commands
http://code.google.com/p/lilypond/issues/detail?id=2872
To expound on comment #11: supported-clefs should likely not be exported. Instead, a function for doing the reverse lookup should be written in the same file, and this function will do the memoization and choice of data structure (again not exported) itself. Then you export this accessor function, and that is what is getting used elsewhere.
