Angular 2 Load data through server API : data.slice error

Im trying to load the data from my API to custom component using Angular2 ng Smart table plugin.

AS per their documentation (https://github.com/akveo/ng2-smart-table/blob/master/src/app/pages/examples/server/basic-example-load.component.ts)

i have my component like:

import { LocalDataSource } from 'ng2-smart-table';
import { ProductService } from '../../../services/product.service';

export class CategoryItemsComponent implements OnInit {

...
 source: LocalDataSource;

 constructor(private productService: ProductService,
             private flashMessage: FlashMessagesService,
             private router: Router,
             http: Http) {
       this.source = new LocalDataSource();

      this.productService.getProductsOncategory(this.categoryid).subscribe((data) => {
      this.source.load(data);
   });

}

ProductService .ts

getProductsOncategory(category_id) {

let catUrl = "http://localhost:5000/products/getProductsOncategory"
let headers = new Headers();
headers.append('Content-Type', 'application/json');
let catIdObj = JSON.stringify({ category_id: category_id })
return this.http.post(catUrl, catIdObj, { headers: headers })
 .map((response: Response) => response.json())
  .do(data => console.log(JSON.stringify(data)))
  .catch(this.handleError);
}

The above API used in the service function works perfect in my postman.

Now i need to load the dame data from that API into my custom component.

I am getting this error:

ERROR TypeError: this.data.slice is not a function

at LocalDataSource.webpackJsonp.../../../../ng2-smart-table/lib/data-source/local/local.data-source.js.LocalDataSource.getElements (http://localhost:4200/1.chunk.js:22280:30) at LocalDataSource.webpackJsonp.../../../../ng2-smart-table/lib/data-source/data-source.js.DataSource.emitOnChanged (http://localhost:4200/1.chunk.js:22185:14) at LocalDataSource.webpackJsonp.../../../../ng2-smart-table/lib/data-source/data-source.js.DataSource.load (http://localhost:4200/1.chunk.js:22105:14) at LocalDataSource.webpackJsonp.../../../../ng2-smart-table/lib/data-source/local/local.data-source.js.LocalDataSource.load (http://localhost:4200/1.chunk.js:22243:38)