Add "not exists" to filters.

[henryxparker]

I realize this is just the docs page but I searched around for a while to figure out where I could give feedback in the app and on official pages and couldn't find anything. So I'll just put it here. If you work at langchain, just send this to the people in charge of that and close this issue.

Langsmith filters needs a "not exists" filter option. It seems like a no-brainer add and shouldn't be too difficult to implement. What if I want to filter out traces that already have feedback for my action so we don't add feedback to a trace more than once. Just strikes me as a very basic filtering option

[hinthornw]

Ya I agree with the utility; the way the queries are executed on the analytical db make this a bit less trivial to implement at scale than what you'd imagine; not saying it's not something we'll support in the future, just a bit of context for why they weren't included in the original implementation.