anchor.diff:     * 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.
  +   * Since isolates run concurrently, it's possible for the receiving isolate
  +   * to exit due to an error, before a request, using this method, has been
  +   * received and processed.
      * To avoid this, either use the corresponding parameter to the spawn
      * function, or start the isolate paused, set errors non-fatal and
      * then resume the isolate.
  
positive.code:    * only one call to `removeOnExitListener` is needed to stop it from receiving
     * exit messagees.
     *
     * Closing the receive port at the end of the send port will not stop the
     * isolate from sending exit messages, they are just going to be lost.
     *
     * An exit message may still be sent if the isolate terminates
     * before this request is received and processed.
  
negative.code:   external void removeOnExitListener(SendPort responsePort);
  
    /**
     * Sets whether uncaught errors will terminate the isolate.
     *
     * If errors are fatal, any uncaught error will terminate the isolate
     * event loop and shut down the isolate.
  