rootConf(key, val) {
    let conf = Conf.getFakeConf();
    const root = this.root();
    if (root && root.type === 'creator') conf = root.conf;

    if (key) {
      if (val !== undefined) conf.setVal(key, val);
      return conf.getVal(key);
    } else {
      return conf;
    }
  }
Get the conf configuration on the logical root node of the instance
If the val parameter is set, the val value of conf is set
@param {string} key - configuration key
@param {any} val - configuration val
@return {object|any} root node
@public