How to add field labels to datasource plugin response

Hello. I’m trying to contribute to an open-source datasource plugin. I found when I try to add “Labels to field” transformation to time-series panels, it shows no available labels. Detailed issue: Time-series unable to add "Labels to fields" transformation · Issue #15 · michelin/snowflake-grafana-datasource · GitHub

I suppose it is because the plugin didn’t add the field label information into the returned data frame. I looked into the tutorial on how to build a data source plugin and datasource API. But I didn’t figure it out which API method should I override, to add the field labels. Could you give me some pointers?

I’m also confused as in the documentation, it says " A data source in Grafana must extend the DataSourceApi interface, which requires you to defines two methods: query and testDatasource .". While in the snowflake plugin I was looking into, it seems they didn’t define these two methods. I’m not sure if it is the documentation is out-of-date or I misunderstood it.

Any help will be much appreciated.