Get experiment list and edit experiment tags

[francoselleskiSH]

There is currently no native method in the SDK to list all experiments or to add a tag to an experiment. The same thing can be accessed through the API but Superhuman wants to interact with Braintrust using a point of contact instead of mixing the SDK and native API calls/

[ibolmo]

Just fyi I've added this to our internal tracking for a previously reported FR. No ETA, yet.

[AbhiPrasad]

This was added in JavaScript with https://github.com/braintrustdata/braintrust-sdk-javascript/releases/tag/js-sdk-v3.1.0. Python PR is here: braintrustdata/braintrust-sdk-python#16. Going to close this as a result, we can track the Python progress with the braintrustdata/braintrust-sdk-python#6 sub issue.