Helm helper to convert label map to comma-separated string

_helper.tpl

{{/*
Convert labels to string like: key1="value1", key2="value2", ...
*/}}
{{- define "chart.external_labels" -}}
{{- $list := list -}}
{{- range $k, $v := .Values.external_labels -}}
{{- $list = append $list (printf "%s=\"%s\"" $k $v) -}}
{{- end -}}
{{ join ", " $list }}
{{- end -}}

values.yaml

---
external_labels:
  cluster-location: lab
  cluster-name: test-cluster01
  

How to convert below template.

{{- define "mongo.selectorLabels" -}}
app: {{ include "mongo.name" . }}
release: {{ .Release.Name }}
{{- end }}

{{- define "sring.lables" -}}
{{- $list := list -}}
{{- range $k, $v := ( include "mongo.selectorLabels" ) -}}
{{- $list = append $list (printf "%s=\"%s\"" $k $v) -}}
{{- end -}}
{{ join ", " $list }}
{{- end -}}