// keeps file open until you cleanUp() the map
static SS zipFileSnippetToLazyTextMap(S snippetID) ctex {
  final ZipFile zip = new ZipFile(loadLibrary(snippetID));
  O f = func(S name) { loadTextFileFromZipFile(zip, name) };
  ret autoCleanUp(new LazyValueTreeMap(listFilesInZip(zip), f) {
    public void finalize() ctex {
      cleanMeUp();
    }
    
    void cleanMeUp() {
      pcall-silent { zip.close(); }
    }
  });
}