MQTT groups : how do can you check?

I’m converting my deconz to MQTT.
Deconz entities can have an attribute: is_deconz_group. If true, it belongs to a deconz group.
Now, I have a few lights that are working with MQTT and put them in a group.
A deconz group is in HA almost an ordenary entity, but it has an attribute: is_deconz_group
a MQTT group seems also to be an ordernart entity, but I don’t see an attribute that let’s me know that it’s a group…
Is there a way to find out?

second question: is it possible to find out what group members a MQTT group has?

thanks in advance