What should be the entities for light.turn_on()?

I am automating the switching on of lights in an area:

id: '1677319029194'
alias: michael ⬤ entrée ⬤ lights on
description: ''
trigger:
  - platform: device
    type: turned_on
    device_id: d4ae80995d09de415c0ab69a04a0a936
    entity_id: switch.michael_michael_main
    domain: switch
condition: []
action:
  - service: script.lights_on_in_area
    data:
      area: michael
mode: single

The service which is called:

lights_on_in_area:
  alias: lights on in area
  sequence:
  - alias: get all lights
    variables:
      area: '{{ area }}'
      lights: '{{ expand(area_entities(area)) | selectattr(''domain'', ''eq'', ''light'')
        | rejectattr(''entity_id'', ''search'', ''restart | disturb | repeat | shuffle'')
        | map(attribute = ''entity_id'') | list }}'
  - alias: turn lights on
    service: light.turn_on
    target:
      entity_id:
      - '{{ lights }}'
  mode: single
  icon: mdi:lightbulb-group

Running the automation ends up with

Template rendered invalid entity IDs: [['light.michael_bureau_droit', 'light.michael_bureau_gauche']]

The devices do exist:

What does this error mean, exactly? The documentation states that entity_id can be a list of entities:

String or list of strings that point at entity_id s of lights.

Ah! I just realized that I created a list of list. The solution is to have

target:
      entity_id: '{{ lights }}'