public static @NotNull Collection<VirtualFile> findFiles(@NotNull String rootTagName,
                                                           @Nullable String namespace,
                                                           @NotNull GlobalSearchScope scope) {
    return FileBasedIndex.getInstance().getContainingFiles(INDEX_ID, new DomIndexKey(rootTagName, ObjectUtils.notNull(namespace, NULL_NAMESPACE)), scope);
  }
public static @NotNull Collection<VirtualFile> findFiles(@NotNull String rootTagName,
                                                           @Nullable String namespace,
                                                           @NotNull GlobalSearchScope scope)