@NotNull
  public JavaModuleSourceRoot combineWith(@NotNull JavaModuleSourceRoot root) {
    List<@Nls(capitalization = Nls.Capitalization.Sentence) String> union = new ArrayList<>(myLanguages.size() + root.myLanguages.size());
    union.addAll(myLanguages);
    union.addAll(root.myLanguages);
    ContainerUtil.removeDuplicates(union);
    return new JavaModuleSourceRoot(getDirectory(), getPackagePrefix(), union);
  }
@NotNull
  public JavaModuleSourceRoot combineWith(@NotNull JavaModuleSourceRoot root)