static @Nullable VirtualFileEnumeration extract(@NotNull GlobalSearchScope scope) {
    if (scope instanceof VirtualFileEnumeration) {
      return (VirtualFileEnumeration)scope;
    }
    if (scope instanceof VirtualFileEnumerationAware) {
      return ((VirtualFileEnumerationAware)scope).extractFileEnumeration();
    }
    return null;
  }
static @Nullable VirtualFileEnumeration extract(@NotNull GlobalSearchScope scope)