class LineApi {
  /**
   * Send a request to LINE API
   * @param {string} endpoint
   * @param {object} payload
   * @return {object} response
   */
  function sendRequest(endpoint, payload) {
    var options = {
      "method": "POST",
      "headers": {
        "Authorization": "Bearer YOUR_ACCESS_TOKEN",
        "Content-Type": "application/json"
      },
      "payload": JSON.stringify(payload)
    };
    var response = UrlFetchApp.fetch("https://api.line.me/v2/" + endpoint, options);
    return JSON.parse(response.getContentText());
  }
}