static MultiMap<S> indexMechLists(LS listNames) {
  MultiMap<S> mm = ciMultiMap();
  for unnull (S name : listNames)
    for (S line : mL(name))
      mm.put(line, name);
  ret mm;
}

static MultiMap<S> indexMechLists(S... listNames) {
  ret indexMechLists(asList(listNames));
}