How to use the @covalent/core.LoadingType.Circular function in @covalent/core

constructor(
    private _titleService: Title,
    private _loadingService: TdLoadingService,
    private _taxService: TaxsService,
    private _userService: UsersService) {
    this._loadingService.create({
      name: 'products',
      type: LoadingType.Circular,
      mode: LoadingMode.Indeterminate,
      color: 'warn',
    });
  }

constructor(
    private _titleService: Title,
    private _loadingService: TdLoadingService,
    private _saltService: SaltsService,
    private _userService: UsersService) {
    this._loadingService.create({
      name: 'products',
      type: LoadingType.Circular,
      mode: LoadingMode.Indeterminate,
      color: 'warn',
    });
  }

constructor(public dialogRef: MdDialogRef,
              private _userService: UsersService,
              private _roleService: RolesService,
              private _loadingService: TdLoadingService,) {
    this._loadingService.create({
      name: 'orders',
      type: LoadingType.Circular,
      mode: LoadingMode.Indeterminate,
      color: 'warn',
    });
  }

constructor(public dialogRef: MdDialogRef,
              private _loadingService: TdLoadingService,
              private _shopService: RetailShopsService,
              private _saltService: SaltsService) {
    this._loadingService.create({
      name: 'salt-form',
      type: LoadingType.Circular,
      mode: LoadingMode.Indeterminate,
      color: 'warn',
    }); }

constructor(
    private _titleService: Title,
    private _loadingService: TdLoadingService,
    private _tagService: TagsService,
    private _userService: UsersService) {
    this._loadingService.create({
      name: 'products',
      type: LoadingType.Circular,
      mode: LoadingMode.Indeterminate,
      color: 'warn',
    });
  }

constructor(public dialogRef: MdDialogRef,
              private _loadingService: TdLoadingService,
              private _shopService: RetailShopsService,
              private _taxService: TaxsService) {
    this._loadingService.create({
      name: 'tax-form',
      type: LoadingType.Circular,
      mode: LoadingMode.Indeterminate,
      color: 'warn',
    }); }

constructor(private _titleService: Title,
              private _loadingService: TdLoadingService,
              private _customerService: CustomerService,
              private _shopService: RetailShopsService,
              private _dialogService: TdDialogService) {
    this._loadingService.create({
      name: 'customer',
      type: LoadingType.Circular,
      mode: LoadingMode.Indeterminate,
      color: 'warn',
    });
  }

constructor(public dialogRef: MdDialogRef,
              private _orderService: OrdersService,
              private _loadingService: TdLoadingService) {
    this._loadingService.create({
      name: 'order-detail',
      type: LoadingType.Circular,
      mode: LoadingMode.Indeterminate,
      color: 'warn',
    });

  }

constructor(
              private _titleService: Title,
              private _loadingService: TdLoadingService,
              private _itemService: ItemsService,
              private _userService: UsersService) {
    this._loadingService.create({
      name: 'products',
      type: LoadingType.Circular,
      mode: LoadingMode.Indeterminate,
      color: 'warn',
    });
  }

constructor(
    private _titleService: Title,
    private _loadingService: TdLoadingService,
    private _distributorService: DistributorService,
    private _userService: UsersService) {
    this._loadingService.create({
      name: 'products',
      type: LoadingType.Circular,
      mode: LoadingMode.Indeterminate,
      color: 'warn',
    });
  }