          <div>
                                  <p>If true, converts nil values into NSNull instance to be presented as <code>null</code> when converted to JSON. Defaults to false.</p>
                                </div>
                              </td>
                            </tr>
                            <tr>
                              <td>
                                <code>
                                <em>rootKey</em>
                                </code>
                    