private static Collection<String> getTopLevelGroupNames(ModuleGrouper grouper) {
    Set<String> topLevelGroupNames = new HashSet<>();
    for (final Module child : grouper.getAllModules()) {
      List<String> group = grouper.getGroupPath(child);
      if (!group.isEmpty()) {
        topLevelGroupNames.add(group.get(0));
      }
    }
    return topLevelGroupNames;
  }
private static Collection<String> getTopLevelGroupNames(ModuleGrouper grouper)