Sensor of count how many lights/switch on

#put this in configuration.yaml
template:
  - sensor:
      - name: "lights_on"
        unique_id: lights_on
        icon: mdi:lightbulb-on
        state: >
          {% set lights = [ 'light.guest_room',
                            'switch.mainbath_left_toolbox',
                            'switch.mainbath_right_mainbath'  #no "," at last entity
                          ] %}
          {{ expand(lights) | selectattr('state','eq','on') | list | count }}