Unable to extract labels from loki sink in vector

[surekha3]

Trying to collect kafka logs using vector latest version and sending to loki. But unable to extract any labels from loglines. when given under labels i.e.,
labels:
env: "{{ env }}"
It's stating function env not found error though it's present within logline. Please help asap

[surekha3]

any help please

[surekha3]

Below is the sink config I used
transforms:
extract_transform:
type: remap
inputs:
- kafka_logs
source: |
.topic = to_string!(.topic)
. = parse_json!(.message)
.host = .parsed.tags.host
sinks:
loki_sink:
type: loki
inputs:
- extract_transform
endpoint: http://loki-nob-gateway
encoding:
codec: "json"
compression: none
healthcheck: false
labels:
job: "kafka"
topic: "{{ topic }}"
host: "{{ host }}"

With this giving error function topic not defined and function host not defined though they're appearing in loglines when printed to console. Logs source is kafka