Conditional light level automation based on event

Configuration
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1

Hi all,

I am trying to capture all events in the light domain, where the brightness is not explicitly set, so that I can adjust the brightness to my required level for the time of day.

Here is the YAML I have ended up with:

alias: Light level automation test
description: ""
trigger:
  - platform: event
    event_type: call_service
    event_data:
      domain: light
      service: turn_on
condition:
  - condition: template
    value_template: "{{ trigger.event.data.service_data.brightness_pct == None }}"
action:
  - service: light.turn_on
    data:
      entity_id: "{{trigger.event.data.service_data.entity_id}}"
      brightness_step_pct: >-
        {{ ((sin((pi / 2) * cos(((now().hour + (now().minute / 60)) / 3.88)
        + 2.8)) * 45) + 55) | int }}
mode: single

The problem I have is this run when the brightness is set in the event, and when it is missing. Clearly my condition is not right, but I can’t work out what I am doing wrong. I also tried:

condition:
  - condition: template
    value_template: "{{ trigger.event.data.service_data.brightness_pct is none }}"

Any pointers?