code: public String getString(String keyName) throws CmsMessageException {
  
          if (m_resourceBundle != null) {
              try {
                  return m_resourceBundle.getString(keyName);
              } catch (MissingResourceException e) {
                  throw new CmsMessageException(
                      Messages.get().container(Messages.ERR_CANT_FIND_RESOURCE_FOR_BUNDLE_2, keyName, m_bundleName));
              }
          } else {
              throw new CmsMessageException(
                  Messages.get().container(Messages.ERR_MESSAGE_BUNDLE_NOT_INITIALIZED_1, m_bundleName));
          }
      }
docs: Directly calls the getString(String) method of the wrapped ResourceBundle.<p>
  
  If you use this this class on a template, you should consider using
  the {@link #key(String)} method to get the value from the ResourceBundle because it
  handles the exception for you in a convenient way.
  
  @param keyName the key
  @return the resource string for the given key
  
  @throws CmsMessageException in case the key is not found or the bundle is not initialized