code: private void initKeySetForXmlBundle() {
  
          // consider only available locales
          for (Locale l : m_locales) {
              if (m_xmlBundle.hasLocale(l)) {
                  Set<Object> keys = new HashSet<Object>();
                  for (I_CmsXmlContentValue msg : m_xmlBundle.getValueSequence("Message", l).getValues()) {
                      String msgpath = msg.getPath();
                      keys.add(m_xmlBundle.getStringValue(m_cms, msgpath + "/Key", l));
                  }
                  m_keyset.updateKeySet(null, keys);
              }
          }
  
      }
docs: Initialize the key set for an xml bundle.