Vaadin Grid toggle tree not working

Hi., I just started using vaadin grid and trying to use vaadin grid toggle tree to display my multi array json object. But iam unable to get children objects on trying to expnad the list. Find my vaading grid structure below and help me where I have done things wrong. Iam not using data-provider. Instead using items=[[data] ]

JSON Structure

import '@vaadin/vaadin-grid/vaadin-grid.js';
import '@vaadin/vaadin-grid/vaadin-grid-selection-column';
import '@vaadin/vaadin-grid/vaadin-grid-sorter';
import '@vaadin/vaadin-grid/vaadin-grid-sort-column';
import '@vaadin/vaadin-grid/vaadin-grid-tree-toggle';

	{'id': 1},
	{'name': 'Book1'},
	{'topics': [
		{'chapter1': [
			{'sub_chapter_1': 'Introduction'},
			{'sub_chapter_2': 'some content2'}
		{'chapter2': [
			{'sub_chapter_1': 'some content 1'},
			{'sub_chapter_2': 'some content 2'}
] = data;

<vaadin-grid aria-label="Tree Data Grid Example" items="[[data]


Expense category


Not sure where I have done wrong. Can you please help me

Hi., any help from community would be appreciated. Tq

Hope no fix for this yet?