matched_instance_distances in sleap.info.metrics does not have default matching function

[eringiglio]

What it says on the tin: I'd like to use sleap.info.metrics.matched_instance_distances in a routine I'm writing to identify low quality user-modified instances. I was delighted to find it in the documentation because I was expecting to need to write my own routine. Unfortunately, it appears to require match_lists_function to be passed to it, and I can't find this function referenced anywhere else in the repository. There's no default matching function listed. Does such a thing exist?

I want to compare predicted and user-generated instances for a specific model so that I can flag user-generated canonical instances that the model does a particularly bad job of predicting, just in case they're rough. In #1516 I have more context on that, but this would be an awesome function for building that except... that there's no clear options for this match_lists_function anywhere I can find on the github.

[roomrys]

I'd just like to point out as a word of warning that although the matched_instance_distances function is shipped with SLEAP, it is not used anywhere in the core package... meaning that it is undertested. #1520 adds a small test and additional development using this function (in regards to #1516) would also ensure/test it's reliability.