@NotNull
  private Map<Group, GroupWrapper> createGroupNodes(@NotNull Collection<? extends Group> groups) {
    Map<Group, GroupWrapper> result = CollectionFactory.createSmallMemoryFootprintMap(groups.size());
    for (Group group : groups) {
      result.put(group, createGroupWrapper(getProject(), group, myTreeModel));
    }
    return result;
  }
@NotNull
  private Map<Group, GroupWrapper> createGroupNodes(@NotNull Collection<? extends Group> groups)