Creating variable in grafana 10 from influxdb fields

Grafana
1

Hello,

I am creating grafana variable from below flux query, from tags.

import "influxdata/influxdb/schema"
schema.tagValues(
    bucket: "Vbuck",
    tag: "Service_Name"
)

I also need to create variable from influxdb fields from a specific measurement.
Influxdb version is v2.7.4

I tried below bu not working

from(bucket: "Vbuck")
  |> range(start: -30d)
  |> filter(fn: (r) => r["_measurement"] == "VMwareRawData14")
  |> group(columns: ["Policy_Type"])
  |> distinct(column: "Policy_Type")
  |> keep(columns: ["Policy_Type"])