code: func translateFederationsofKubeDNSToCoreDNS(dataField, coreDNSDomain string, kubeDNSConfigMap *v1.ConfigMap) (string, error) {
  	if kubeDNSConfigMap == nil {
  		return "", nil
  	}
  
  	if federation, ok := kubeDNSConfigMap.Data[dataField]; ok {
  		var (
  			federationStanza []interface{}
  			body             [][]string
  		)
  		federationData := make(map[string]string)
  
  		err := json.Unmarshal([]byte(federation), &federationData)
  		if err != nil {
  			return "", errors.Wrap(err, "failed to parse JSON from kube-dns ConfigMap")
  		}
  		fStanza := map[string]interface{}{}
  
  		for name, domain := range federationData {
  			body = append(body, []string{name, domain})
  		}
  		federationStanza = append(federationStanza, fStanza)
  		fStanza["keys"] = []string{"federation " + coreDNSDomain}
  		fStanza["body"] = body
  		stanzasBytes, err := json.Marshal(federationStanza)
  		if err != nil {
  			return "", err
  		}
  
  		corefileStanza, err := caddyfile.FromJSON(stanzasBytes)
  		if err != nil {
  			return "", err
  		}
  
  		return prepCorefileFormat(string(corefileStanza), 8), nil
  	}
  	return "", nil
  }
docs: // translateFederationsofKubeDNSToCoreDNS translates Federations Data in kube-dns ConfigMap
  // to Federation for CoreDNS Corefile.