@NotNull
  private static Set<VirtualFile> collectSdkClasses(Set<? extends Sdk> sdks) {
    Set<VirtualFile> roots = new HashSet<>();

    for (Sdk sdk : sdks) {
      roots.addAll(Arrays.asList(sdk.getRootProvider().getFiles(OrderRootType.CLASSES)));
    }
    return roots;
  }
@NotNull
  private static Set<VirtualFile> collectSdkClasses(Set<? extends Sdk> sdks)