JupyterLab: How to trigger a call back function to python backend from Javascript front end - jupyter-notebook

Question

I am trying to build a JupyterLab Widget extension
I create an 'example.js' file that holds a button execute and an 'example.py' which holds model information.
When I run the code bellow,
import ExampleWidget
from ExampleWidet import example
example.RunTool()
Creates a button,
I want to execute another python function in the backend from the button click event.
I am not able to find a way to implement this part please help.
thanks
Update
Python Code:
from ipywidgets import VBox, widget_serialization
from traitlets import Unicode, List, Dict, Instance
from ._frontend import module_name, module_version
#from .basewidget import BaseWidget
class ExampleUIOutput(UIOutput):
"""
Widget used to render Python output in a UI
"""
_model_name = Unicode('ExampleUIOutputModel').tag(sync=True)
_model_module = Unicode(module_name).tag(sync=True)
_model_module_version = Unicode(module_version).tag(sync=True)
_view_name = Unicode('ExampleUIOutputView').tag(sync=True)
_view_module = Unicode(module_name).tag(sync=True)
_view_module_version = Unicode(module_version).tag(sync=True)
name = Unicode('Python Results').tag(sync=True)
def __init__(self, **kwargs):
# Initialize the child widget container
self.appendix = VBox()
UIOutput.__init__(self, **kwargs)
Javascript Code:
export class ExampleUIOutputModel extends UIOutputModel {
defaults() {
return Object.assign(Object.assign({}, super.defaults()), { _model_name: ExampleUIOutputModel.model_name, _model_module: ExampleUIOutputModel.model_module, _model_module_version: ExampleUIOutputModel.model_module_version, _view_name: ExampleUIOutputModel.view_name, _view_module: ExampleUIOutputModel.view_module, _view_module_version: ExampleUIOutputModel.view_module_version, name: 'Python Results' });
}
}
ExampleUIOutputModel.model_name = 'ExampleUIOutputModel';
ExampleUIOutputModel.model_module = MODULE_NAME;
ExampleUIOutputModel.model_module_version = MODULE_VERSION;
ExampleUIOutputModel.view_name = 'ExampleUIOutputView';
ExampleUIOutputModel.view_module = MODULE_NAME;
ExampleUIOutputModel.view_module_version = MODULE_VERSION;
ExampleUIOutputModel.serializers = Object.assign(Object.assign({}, UIOutputModel.serializers), { appendix: {
deserialize: (value, manager) => unpack_models(value, manager)
} });
export class ExampleUIOutputView extends UIOutputView {
constructor() {
super(...arguments);
}
render() {
const Hello = document.createElement('button')
this.el.append(Hello)
Hello.addEventListener("click", function() {
console.log('Hello World');
}, false);
}
}
Utilities:
I have a python file Utils.py with the code for example
def HelloWorld(name):
print('Hello '+name)
I want when I click the button it executes this python code or any other python code.