// optional parameter trace_out for collecting the reference tree
// optional parameter exclude: set of excluded
static Set<S> recursivelyCollectSnippetIDsFromTranspiled(S snippetID, O... _) {
  Set<S> exclude = cast optPar exclude(_);
  ret transitiveHullOfFunction(func(S snippetID) -> Collection<S> {
    collectionMinusSet(collectSnippetIDsInTranspiledSnippet(snippetID), exclude)
  }, snippetID, _);
}