anchor.diff:    external void addOnExitListener(SendPort responsePort, {Object response});
   
     /**
  -   * Stop listening for exit messages from the isolate.
  +   * Stops listening for exit messages from the isolate.
      *
      * Requests for the isolate to not send exit messages on [responsePort].
      * If the isolate isn't expecting to send exit messages on [responsePort],
  
positive.code:    * Listening using the same port more than once does nothing.
     * A port will only receive each error once,
     * and will only need to be removed once using [removeErrorListener].
     *
     * Since isolates run concurrently, it's possible for it to exit before the
     * error listener is established. To avoid this, start the isolate paused,
  
negative.code:   external void kill({int priority: BEFORE_NEXT_EVENT});
  
    /**
     * Requests that the isolate send [response] on the [responsePort].
     *
     * The [response] object must follow the same restrictions as enforced by
     * [SendPort.send].
  