code: public static @Nonnull JSONObject getBundle(@Nonnull String baseName, @Nonnull Locale locale) throws MissingResourceException {
          String bundleKey = baseName + ":" + locale.toString();
          JSONObject bundleJSON = bundles.get(bundleKey);
  
          if (bundleJSON != null) {
              return bundleJSON;
          }
  
          ResourceBundle bundle = getBundle(baseName, locale, Jenkins.class.getClassLoader());
          if (bundle == null) {
              // Not in Jenkins core. Check the plugins.
              Jenkins jenkins = Jenkins.getInstance(); // will never return null
              if (jenkins != null) {
                  for (PluginWrapper plugin : jenkins.getPluginManager().getPlugins()) {
                      bundle = getBundle(baseName, locale, plugin.classLoader);
                      if (bundle != null) {
                          break;
                      }
                  }
              }
          }
          if (bundle == null) {
              throw new MissingResourceException("Can't find bundle for base name "
                      + baseName + ", locale " + locale, baseName + "_" + locale, "");
          }
  
          bundleJSON = toJSONObject(bundle);
          bundles.put(bundleKey, bundleJSON);
  
          return bundleJSON;
      }
docs: Get a bundle JSON using the supplied Locale.
  @param baseName The bundle base name.
  @param locale The Locale.
  @return The bundle JSON.
  @throws MissingResourceException Missing resource bundle.