How to use the @google-cloud/monitoring.AlertPolicyServiceClient function in @google-cloud/monitoring

async function restorePolicies(projectId) {
  // Note: The policies are restored one at a time because I get 'service
  //       unavailable' when I try to create multiple alerts simultaneously.
  // [START monitoring_alert_restore_policies]
  // [START monitoring_alert_create_policy]
  const fs = require('fs');

  // Imports the Google Cloud client library
  const monitoring = require('@google-cloud/monitoring');

  // Creates a client
  const client = new monitoring.AlertPolicyServiceClient();

  /**
   * TODO(developer): Uncomment the following lines before running the sample.
   */
  // const projectId = 'YOUR_PROJECT_ID';

  console.log('Loading policies from ./policies_backup.json');
  const fileContent = fs.readFileSync('./policies_backup.json', 'utf-8');
  const policies = JSON.parse(fileContent);

  for (const index in policies) {
    // Restore each policy one at a time
    let policy = policies[index];
    if (await doesAlertPolicyExist(policy.name)) {
      policy = await client.updateAlertPolicy({alertPolicy: policy});
    } else {

async function listPolicies(projectId) {
  // [START monitoring_alert_list_policies]
  // Imports the Google Cloud client library
  const monitoring = require('@google-cloud/monitoring');

  // Creates a client
  const client = new monitoring.AlertPolicyServiceClient();

  /**
   * TODO(developer): Uncomment the following lines before running the sample.
   */
  // const projectId = 'YOUR_PROJECT_ID';

  const listAlertPoliciesRequest = {
    name: client.projectPath(projectId),
  };
  const [policies] = await client.listAlertPolicies(listAlertPoliciesRequest);
  console.log('Policies:');
  policies.forEach(policy => {
    console.log(`  Display name: ${policy.displayName}`);
    if (policy.documentation && policy.documentation.content) {
      console.log(`     Documentation: ${policy.documentation.content}`);
    }

async function backupPolicies(projectId) {
  // [START monitoring_alert_backup_policies]
  const fs = require('fs');

  // Imports the Google Cloud client library
  const monitoring = require('@google-cloud/monitoring');

  // Creates a client
  const client = new monitoring.AlertPolicyServiceClient();

  /**
   * TODO(developer): Uncomment the following lines before running the sample.
   */
  // const projectId = 'YOUR_PROJECT_ID';

  const listAlertPoliciesRequest = {
    name: client.projectPath(projectId),
  };

  let [policies] = await client.listAlertPolicies(listAlertPoliciesRequest);

  // filter out any policies created by tests for this sample
  policies = policies.filter(policy => {
    return !policy.displayName.startsWith('gcloud-tests-');
  });

async function replaceChannels(projectId, alertPolicyId, channelIds) {
  // [START monitoring_alert_replace_channels]
  // [START monitoring_alert_enable_channel]
  // [START monitoring_alert_update_channel]
  // [START monitoring_alert_create_channel]

  // Imports the Google Cloud client library
  const monitoring = require('@google-cloud/monitoring');

  // Creates clients
  const alertClient = new monitoring.AlertPolicyServiceClient();
  const notificationClient = new monitoring.NotificationChannelServiceClient();

  /**
   * TODO(developer): Uncomment the following lines before running the sample.
   */
  // const projectId = 'YOUR_PROJECT_ID';
  // const alertPolicyId = '123456789012314';
  // const channelIds = [
  //   'channel-1',
  //   'channel-2',
  //   'channel-3',
  // ];

  const notificationChannels = channelIds.map(id =>
    notificationClient.notificationChannelPath(projectId, id)
  );

async function enablePolicies(projectId, enabled, filter) {
  // [START monitoring_alert_enable_policies]
  // Imports the Google Cloud client library
  const monitoring = require('@google-cloud/monitoring');

  // Creates a client
  const client = new monitoring.AlertPolicyServiceClient();

  /**
   * TODO(developer): Uncomment the following lines before running the sample.
   */
  // const projectId = 'YOUR_PROJECT_ID';
  // const enabled = true;
  // const filter = 'A filter for selecting policies, e.g. description:"cloud"';

  const listAlertPoliciesRequest = {
    name: client.projectPath(projectId),
    // See https://cloud.google.com/monitoring/alerting/docs/sorting-and-filtering
    filter: filter,
  };

  const [policies] = await client.listAlertPolicies(listAlertPoliciesRequest);
  const tasks = await Promise.all(