Kapacitor get tag value

Hi, I am using Tickscript and my purpose is to run the python script if the value is 0. Below is my code:

var data = batch
    from(bucket: "bucket_name")
  |> range(start: -3h)
  |> filter(fn: (r) => r["_measurement"] == "measurement_name")
  |> filter(fn: (r) => r["_field"] == "field_name")
  |> filter(fn: (r) => r["_value"] > 0)
  |> truncateTimeColumn(unit: 1h)

var alert = data
      .crit(lambda: "_value" > 0)
      .exec('python3', 'python-file-location', '--node', '{{ index .Fields "_value" }}')

I was trying to use template and pass a random parameter, However I am getting “{{ index .Fields “_value” }}” in python file instead of some actual string. My requirement is to pass value of tag column say “A” as an argument to python file. How can I get that value.