private static @Nullable <T> Map<String, T> getMap(@NotNull Map<String, Map<String, T>> resources, @Nullable String version) {
    version = Strings.notNullize(version, DEFAULT_VERSION);
    Map<String, T> map = resources.get(version);
    return map == null && !version.equals(DEFAULT_VERSION) ? resources.get(DEFAULT_VERSION) : map;
  }
private static @Nullable <T> Map<String, T> getMap(@NotNull Map<String, Map<String, T>> resources, @Nullable String version)