Meaning of first empty column in CSV API result

I’m always getting an empty field for all CSV rows I get from an API flux query. Where it is documented ? How can I use it ?

Here is my sample results



Please can you show us the query you are using?


    from(bucket: "test")
        |> range(start: -20m, stop: now ())
        |> filter(fn: (r) => r["_measurement"] == "cpu_load_short")
        |> filter(fn: (r) => r["host"] == "server01")
        |> keep (columns: ["_time", "_field", "_value", "region"])
        |> yield (name: "hello")