code: private void parseLanguageAliases(JsonObject root) {
      JsonObject node = resolve(root, "supplemental", "metadata", "alias", "languageAlias");
      for (String tag : objectKeys(node)) {
        JsonObject value = node.getAsJsonObject(tag);
        String replacement = string(value, "_replacement");
        languageAliases.put(tag, replacement);
      }
    }
docs: Parse the supplemental language aliases map.