code: public static synchronized void onDestroy(Context context) {
          if (sRetryReceiver != null) {
              Log.v(TAG, "Unregistering receiver");
              context.unregisterReceiver(sRetryReceiver);
              sRetryReceiver = null;
          }
      }
docs: Clear internal resources.
  
  <p>
  This method should be called by the main activity's {@code onDestroy()}
  method.