#!/usr/bin/env python3 from nicegui import ui tree = ui.tree([ {'id': 'numbers', 'icon': 'tag', 'children': [{'id': '1'}, {'id': '2'}]}, {'id': 'letters', 'icon': 'text_fields', 'children': [{'id': 'A'}, {'id': 'B'}]}, ], label_key='id', on_select=lambda e: ui.notify(e.value)) tree.add_slot('default-header', r'''