static Pair<S, LS> extractLibsFromTranspilation(S transpiledSrc) {
  if (transpiledSrc == null) transpiledSrc = "";
  int i = transpiledSrc.indexOf('\n');
  S dehlibs = substring(transpiledSrc, 0, i);
  transpiledSrc = transpiledSrc.substring(i+1);
  new L<S> libs;
  Matcher matcher = Pattern.compile("\\d+").matcher(dehlibs);
  while (matcher.find())
    libs.add(fsI(matcher.group()));
  ret pair(transpiledSrc, libs);
}

Began life as a copy of #1011367