anchor.diff:     * stack trace, or `null` if no stack trace was provided.
      * To convert this back to a [StackTrace] object, use [StackTrace.fromString].
      *
  -   * Listening using the same port more than once does nothing. It will only
  -   * get each error once.
  +   * 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,
  
positive.code:   external void addOnExitListener(SendPort responsePort, {Object response});
  
    /**
     * Stop listening on exit messages from the isolate.
     *
     * If a call has previously been made to [addOnExitListener] with the same
     * send-port, this will unregister the port, and it will no longer receive
     * a message when the isolate terminates.
     * A response may still be sent until this operation is fully processed by
     * the isolate.
     */
    external void removeOnExitListener(SendPort responsePort);
  
  
negative.code:    * event loop and shut down the isolate.
     *
     * This call requires the [terminateCapability] for the isolate.
     * If the capability is absent or incorrect, no change is made.
     *
     * Since isolates run concurrently, it's possible for it to exit due to an
     * error before errors are set non-fatal.
  