Not yet. But I hope to at least motivate somebody with more skills in the trade to propose a filter. I have not coded a tree myself and other people are saying a bloom filter is more efficient for this need. No idea which is better.
Discussion
A bit filter would be much better. The only issue is there are false positives. So occasionally you would send a filter to a relay and it would think you already have some event that you dont. You can tune the false positive rate though.
False negatives are fine (receiving an event you already have). False positives (not sending info the user expects to see) are a big no.