Using existing group in custom component

Can anyone point me in the right direction here - tried searching, tried a few things and having trouble finding the right syntax…

I want to create a custom component that listens for state changes of a group of sensors. The sensors are already grouped - i.e. in my group.yaml I have something like:

mysensors:
  name: "My sensors"
  entities:
    - sensor.sensor1
    - sensor.sensor2

etc…

I can get my custom component working if define it in configuration.yaml like this:

my_custom_component:
  sensors:
    - sensor.sensor1
    - sensor.sensor2

And then in the custom component python code:

sensors = config[DOMAIN]['sensors']

And:

track_state_changes(hass, temperatures, state_changed)

What I’d like to do is configure my component like this:

my_custom_component:
  sensor_group: mysensors

That way I don’t have to repeat my sensor list (DRY and all that!)

Then in the code:

sensorgroup = config[DOMAIN]['sensor_group']

My question is how do I expand that group to its list of entity_ids to pass as the array to track_state_change?

I’m hoping it’s something really obvious that I’ve missed, but I can’t seem to figure out how.