code: public void unregisterExtension(String keyStr) throws NotFound, RuntimeFault, RemoteException {
          if (keyStr == null) {
              throw new NullPointerException();
          }
          getVimService().unregisterExtension(getMOR(), keyStr);
      }
docs: Un-register an existing plugin If <code>keyStr</code> is null then a
  <code>NullPointerException</code> is thrown.
  
  @param keyStr The unique key of the plugin
  @throws RemoteException
  @throws RuntimeFault
  @throws NotFound        either because of the web service itself, or because of the
  service provider unable to handle the request.