How to debug variable objects?

Configuration Blueprints
1

Hello,

I’m trying to integrate a push notification + an image with the Nest integration. So I’m following the doc here Nest - Home Assistant

I have this config, pasted from the automation debugger :

id: '1654354718834'
alias: Notif détection sonnette
description: ''
trigger:
  - platform: device
    device_id: 3ed7e1fc3a0a1e96dbda4d83f73d6112
    domain: nest
    type: camera_motion
condition: []
action:
  - device_id: dfc48ab7e364510ace4abf60c6589072
    domain: mobile_app
    type: notify
    message: Someone is here !
    title: Ding dong
    data:
      image: >-
        /api/nest/event_media/{{ trigger.event.data.device_id }}/{{
        trigger.event.data.nest_event_id }}/thumbnail
mode: single

And when i’m executing the automation, I got the following error message :

Error: Error rendering data: UndefinedError: 'dict object' has no attribute 'event'

So I understand that the event property is not existing in the trigger object, but that does not help me more.

Is there a way to dump the whole trigger object or something else in order to understand how are the object / graph structure ?

Thanks !