Hi. It’s me again.
Coming to you awesome people looking for help regarding Template Light. I’m still quite new in the templating business.
After i have had problems with getting my IKEA Tradri Groups working in this thread i set the option “allow_tradfri_groups” in my config to “false” but i would still love to group my lights so i don’t have to type multiple entity ID’s into my automations and i felt like Template Light could do the job. 
Parsing brightness to the Template Light as shown below work but only when the individual lights are one. I get this error in the log:
2017-11-14 07:38:41 ERROR (MainThread) [homeassistant.components.light.template] UndefinedError: ‘mappingproxy object’ has no attribute ‘brightness’
2017-11-14 07:38:41 ERROR (MainThread) [homeassistant.helpers.entity] Update for light.hallway fails
Traceback (most recent call last):
File “/usr/lib/python3.6/site-packages/homeassistant/helpers/entity.py”, line 204, in async_update_ha_state
yield from self.async_device_update()
File “/usr/lib/python3.6/site-packages/homeassistant/helpers/entity.py”, line 307, in async_device_update
yield from self.async_update()
File “/usr/lib/python3.6/asyncio/coroutines.py”, line 210, in coro
res = func(*args, **kw)
File “/usr/lib/python3.6/site-packages/homeassistant/components/light/template.py”, line 264, in async_update
if 0 <= int(brightness) <= 255:
Turning off the light.group does not work, it turns back on instantly but turns off the individual lights.
platform: template
lights:
hallway:
friendly_name: "Light Hallway"
value_template: >-
{% if is_state('light.hallway_panel_1', 'on') and is_state('light.hallway_panel_2', 'on') %}
on
{% else %}
off
{% endif %}
turn_on:
service: light.turn_on
entity_id:
- light.hallway_panel_1
- light.hallway_panel_2
turn_off:
service: light.turn_off
entity_id:
- light.hallway_panel_1
- light.hallway_panel_2
level_template: >-
{% if is_state('light.hallway', 'on') %}
{{ (states.light.hallway_panel_1.attributes.brightness)|int }}
{% else %}
0
{% endif %}
set_level:
service: light.turn_on
data_template:
entity_id:
- light.hallway_panel_1
- light.hallway_panel_2
brightness: "{{ brightness }}"
transition: "{{ transition }}"
Any help would be much appreciated as i am eager to learn this! 