Parse logs for specific container to add labels

I deployed Loki and Promtail using the grafana Helm Chart and I struggle to configure it.

As a simple configuration, I would like to add a specific label (an UUID). To do so, I use the specific yaml :

config:
  lokiAddress: http://loki-headless.admin:3100/loki/api/v1/push
  snippets:
      extraScrapeConfigs: |
        - job_name: dashboard
          kubernetes_sd_configs:
            - role: pod
          pipeline_stages:
            - docker: {}
            - match:
                selector: '{container = "dashboard"}'
                stages:
                  - regex:
                      expression: '(?P<loguuid>[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12})'
                  - labels:
                      loguuid:

Which is deployed with the command: helm upgrade -install promtail -n admin grafana/promtail -f promtail.yaml

Of course, I still don’t have the label in grafana. Can someone tell me what I did wrong?