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

// Debug log messages enabled? (true/false)
var debugMode = process.env.DEBUG || false;
var dryRunMode = process.env.DRYRUN || false;

// --------------------------------------------------------------------------------------
// SECTION: Initialization
// This code sets configuration values and retrieves the server state from a JSON file
// --------------------------------------------------------------------------------------
//
const dataFilePath = './scripts/data.json'
var JSONData = require( dataFilePath);    // Reads the JSON data file to get current server state

// Google Stackdriver Monitoring initialization
if (!dryRunMode) var {google} = require('googleapis');
if (!dryRunMode) var monitoring = require('@google-cloud/monitoring');
if (!dryRunMode) var client = new monitoring.MetricServiceClient();
var projectId = "";
var pod_guid = "";
var namespace_name = "";
var zone_name = "";
var cluster_name = "";
var pod_name = "";

// Initialize the JSON file to false and 0 users
var cpuLoadRunning = false;
var customMetricCreated = false;
var userCount = 0;
JSONData.CpuLoadRunning = cpuLoadRunning;
JSONData.customMetricCreated = customMetricCreated;
JSONData.UserCount = userCount;
JSONData.DebugMode = debugMode;
setTimeout(initData, 2000);	// Wait for the file to be ready, then initialize its contents

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

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

  /**
   * TODO(developer): Uncomment and edit the following lines of code.
   */
  // const projectId = 'YOUR_PROJECT_ID';
  // const resourceType = 'some_resource_type, e.g. cloudsql_database';

  const request = {
    name: client.monitoredResourceDescriptorPath(projectId, resourceType),
  };

  // Lists monitored resource descriptors
  const [descriptor] = await client.getMonitoredResourceDescriptor(request);

  console.log(`Name: ${descriptor.displayName}`);
  console.log(`Description: ${descriptor.description}`);

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

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

  /**
   * TODO(developer): Uncomment and edit the following lines of code.
   */
  // const projectId = 'YOUR_PROJECT_ID';

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

  // Lists metric descriptors
  const [descriptors] = await client.listMetricDescriptors(request);
  console.log('Metric Descriptors:');
  descriptors.forEach(descriptor => console.log(descriptor.name));

  // [END monitoring_list_descriptors]

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

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

  /**
   * TODO(developer): Uncomment and edit the following lines of code.
   */
  // const projectId = 'YOUR_PROJECT_ID';
  // const metricId = 'custom.googleapis.com/stores/daily_sales';

  const request = {
    name: client.metricDescriptorPath(projectId, metricId),
  };

  // Deletes a metric descriptor
  const [result] = await client.deleteMetricDescriptor(request);
  console.log(`Deleted ${metricId}`, result);

  // [END monitoring_delete_metric]

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

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

  /**
   * TODO(developer): Uncomment and edit the following lines of code.
   */
  // const projectId = 'YOUR_PROJECT_ID';

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

  // Lists monitored resource descriptors
  const [descriptors] = await client.listMonitoredResourceDescriptors(request);
  console.log('Monitored Resource Descriptors:');
  descriptors.forEach(descriptor => {
    console.log(descriptor.name);
    console.log(`  Type: ${descriptor.type}`);

async function quickstart() {
  // Your Google Cloud Platform project ID
  const projectId = process.env.GCLOUD_PROJECT || 'YOUR_PROJECT_ID';

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

  // Prepares an individual data point
  const dataPoint = {
    interval: {
      endTime: {
        seconds: Date.now() / 1000,
      },
    },
    value: {
      // The amount of sales
      doubleValue: 123.45,
    },
  };

  // Prepares the time series request
  const request = {

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

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

  /**
   * TODO(developer): Uncomment and edit the following lines of code.
   */
  // const projectId = 'YOUR_PROJECT_ID';

  const request = {
    name: client.projectPath(projectId),
    metricDescriptor: {
      description: 'Daily sales records from all branch stores.',
      displayName: 'Daily Sales',
      type: 'custom.googleapis.com/stores/daily_sales',
      metricKind: 'GAUGE',
      valueType: 'DOUBLE',
      unit: '{USD}',
      labels: [

try {
                await metricServiceClient.createTimeSeries(writeRequest);
                node.send(msg);
            } catch(err) {
                node.error(err);
            }
        } // Input

        // We must have EITHER credentials or a keyFilename.  If neither are supplied, that
        // is an error.  If both are supplied, then credentials will be used.
        if (credentials) {
            metricServiceClient = new monitoring.MetricServiceClient({
                "credentials": credentials
            });
        } else if (keyFilename) {
            metricServiceClient = new monitoring.MetricServiceClient({
                "keyFilename": keyFilename
            });
        } else {
            metricServiceClient = new monitoring.MetricServiceClient({});
        }

        node.on('input', Input);
    } // MonitoringNode