@NotNull
  private static List<? extends IndexableIteratorBuilder> createLibraryIteratorBuilders(@NotNull SyntheticLibraryDescriptor beforeLib,
                                                                                        @NotNull SyntheticLibraryDescriptor afterLib) {
    Collection<VirtualFile> newRoots = ContainerUtil.subtract(afterLib.getAllRoots(), beforeLib.getAllRoots());
    if (!newRoots.isEmpty()) {
      return Collections.singletonList(
        new SyntheticLibraryIteratorBuilder(afterLib.library, afterLib.presentableLibraryName, newRoots));
    }
    else {
      return Collections.emptyList();
    }
  }
@NotNull
  private static List<? extends IndexableIteratorBuilder> createLibraryIteratorBuilders(@NotNull SyntheticLibraryDescriptor beforeLib,
                                                                                        @NotNull SyntheticLibraryDescriptor afterLib)