How can i return a list value in button card template?

orginal code , i wanna return a list value inside button card template.

          cards:
            - type: custom:button-card
              color_type: label-card
              color: rgb(44, 109, 214)
              entity: light.bed_light
              template: |
                 [[[ return variables.icon ]]]
template: |
   [[[ return variables.icon_1 ]]]

Output passed in button card template :

template: light_white

Failed:	
template: |
  - [[[ return variables.icon_1 ]]]
  - [[[ return variables.icon_2 ]]]

how can i do to output a list just like below?

template: 
  - light_white
  - light_rgb