Apollo graphql server subscription - send only if data differs

So I asked this question on stackoverflow, unfortunatly to no result.

I couldn’t find anything in the docs, but I’d like to compare the last sent message of a subscription to the current message and only send it out, if it differs.

If I could simply compare the actual “over the wire” JSON message sent out to the specific subscriber with the “about to be sent” message this would be very simple.

Any idea on how to accomplish that?