@NotNull
  public static Set<VirtualFile> getProjectRootsToIndex(@NotNull IndexableSetContributor contributor, @NotNull Project project) {
    Set<VirtualFile> roots = contributor.getAdditionalProjectRootsToIndex(project);
    return filterOutNulls(contributor, "getAdditionalProjectRootsToIndex(Project)", roots);
  }
@NotNull
  public static Set<VirtualFile> getProjectRootsToIndex(@NotNull IndexableSetContributor contributor, @NotNull Project project)