wijmo.angular2.grid.filter is an external TypeScript module that can be imported to your code using its ambient module name. For example:

import * as wjFilter from 'wijmo/wijmo.angular2.grid.filter';
import * as wjGrid from 'wijmo/wijmo.angular2.grid';
 
@Component({
    directives: [wjGrid.WjFlexGrid, wjFilter.WjFlexGridFilter],
    template: `
      <wj-flex-grid [itemsSource]="data">
          <wj-flex-grid-filter [filterColumns]="['country', 'expenses']"></wj-flex-grid-filter>
      </wj-flex-grid>`,
    selector: 'my-cmp',
})
export class MyCmp {
    data: any[];
}