Graph componente - legend

ESPHome
1

I want to show a graph with legend on an ILI9488 display, I have following code snippet:

graph:
  - id: single_temperature_graph
    sensor: balkon_currentpower
    duration: 1h
    width: 380
    height: 300
    line_thickness: 2
    line_type: SOLID
    legend:
      - show_units: True
      - show_values: BESIDE
      - name_font: my_font_20

but get the following error:

Failed config

graph: [source /config/esphome/display2.yaml:77]
  - id: single_temperature_graph
    sensor: balkon_currentpower
    duration: 1h
    width: 380
    height: 300
    line_thickness: 2
    line_type: SOLID
    legend:
      
      'name_font' is a required option for [0].
      - show_units: True
      - show_values: BESIDE
      - name_font: my_font_20

I did not find any sample or reference for “name_font” - any hints how to use it?
Colors and fonts aer defined and used in other parts of the script.

thanks!