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 resume(Capability resumeCapability);
  
    /**
     * Asks the isolate to send [response] on [responsePort] when it terminates.
     *
     * The isolate will send a `response` message on `responsePort` as the last
     * thing before it terminates. It will run no further code after the message
     * has been sent.
     *
     * Adding the same port more than once will only cause it to receive one
     * message, using the last response value that was added.
     *
     * If the isolate is already dead, no message will be sent.
     *
     * The [response] object must follow the same restrictions as enforced by
     * [SendPort.send].
  
negative.code:    *
     * * `IMMEDIATE`: The isolate responds as soon as it receives the
     *     control message. This is after any previous control message
     *     from the same isolate has been received and processed,
     *     but may be during execution of another event.
     * * `BEFORE_NEXT_EVENT`: The response is scheduled for the next time
     *     control returns to the event loop of the receiving isolate,
     *     after the current event, and any already scheduled control events,
  