How to use the @azure/arm-appservice.WebSiteManagementClient function in @azure/arm-appservice

public constructor(serverless: Serverless, options: Serverless.Options) {
    super(serverless, options);

    this.webClient = new WebSiteManagementClient(this.credentials, this.subscriptionId);
    this.blobService = new AzureBlobStorageService(serverless, options);
  }

constructor(clientId, clientSecret, tenantId, subscriptionId) {

        this.clientId = clientId;
        this.clientSecret = clientSecret;
        this.tenantId = tenantId;
        this.subscriptionId = subscriptionId;

        this.classList = new Map();
        this.classList.set('WebSiteManagementClient', WebSiteManagementClient);
        this.classList.set('ResourceManagementClient', ResourceManagementClient);
        this.classList.set('StorageManagementClient', StorageManagementClient);
        this.classList.set('ApiManagementClient', ApiManagementClient);
        this.classList.set('CdnManagementClient', CdnManagementClient);
        this.classList.set('CosmosDBManagementClient', CosmosDBManagementClient);
        this.classList.set('EventHubManagementClient', EventHubManagementClient);
        this.classList.set('ServiceBusManagementClient', ServiceBusManagementClient);

        this.instanceList = new Map();
    }

export async function login(): Promise {
  const creds = await msRestNodeAuth.loginWithServicePrincipalSecret(clientId, secret, tenant)
  const websites = new appservice.WebSiteManagementClient(creds as any, subscriptionId)
  return {
    websites,
    webapps: new appservice.WebApps(websites),
    secrets: new SecretClient(`https://majavashakki-vault.vault.azure.net`, new EnvironmentCredential()),
    cosmosdb: new cosmosdb.CosmosDBManagementClient(creds as any, subscriptionId),
    containerregistry: new ContainerRegistryManagementClient(creds as any, subscriptionId),
  }
}