Javascript 导航Khan学院主题树

我正在尝试使用谷歌应用程序脚本访问Khan Academy服务器，并计算掌握给定主题所需的技能数量。例如，我希望能够获得掌握代数1所需的技能数量。我如何使用“topictree”实现这一点？我已经成功访问了Khan Academy服务器，打印出主题树的内容没有问题——我只需要知道所需技能的信息存储在哪里。谢谢

function listExercises() {
  var service = getKhanAcademyService();
  if (service.hasAccess()) {

    var response = service.fetch('https://www.khanacademy.org/api/v1/topictree');
    Logger.log(response);

    //----Here I would like to navigate to a specific topic (like Algebra 1) 
    in the topic tree and retrieve how many skills are required to master it-- //

  } else {
    var authorizationUrl = service.authorize();
    Logger.log('Please visit the following URL and then re-run the script: ' + authorizationUrl);
  }
}