Azure Resource Graph - get all functions of a function app

Hi, 

I'm new with Azure Resource Graph, and I'm trying to get all the functions from a function app. 

Firstly, I created a query to get the function apps : 

resources
| where type == 'microsoft.web/sites'
| where properties['kind'] == 'functionapp'

Then I searched in the function app properties if functions were listed, but there are no information about it. 
So, I inspected the JSON definition of one function contained in a function app, and the type of the resource is "Microsoft.Web/sites/functions". But when I run a query using the type I get no results. 

How should I do to get the functions contained in a function app using Azure Resource Graph ?

Thank you