return err
	}

	if err != nil {
		return err
	}
	for _, c := range ctx.Clusters() {
		ingr = append(ingr, ist.IngressFor(c))
	}
	mockProm = match.ServiceName(echo.NamespacedName{Name: "mock-prom", Namespace: apps.Namespace}).GetMatches(apps.Echos().All.Instances())
	promInst, err = prometheus.New(ctx, prometheus.Config{})

	if svc.Spec.ClusterIP != "" && svc.Spec.ClusterIP != v1.ClusterIPNone {
		res = append(res, svc.Spec.ClusterIP)
	}
	for _, ing := range svc.Status.LoadBalancer.Ingress {
		// IPs are strictly optional for loadbalancers - they may just have a hostname.
		if ing.IP != "" {
			res = append(res, ing.IP)
		}
	}
	return res

				return service.Spec.ClusterIPs[idx]
			}
		}
	}

	return ""
}

func IsVIPMode(ing v1.LoadBalancerIngress) bool {
	if !utilfeature.DefaultFeatureGate.Enabled(features.LoadBalancerIPMode) {
		return true // backwards compat
	}
	if ing.IPMode == nil {
		return true
	}
	return *ing.IPMode == v1.LoadBalancerIPModeVIP

// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// As of "Mon 6 Nov 2017", run.go doesn't yet have proper
// column matching so instead match the output manually
// by exec-ing

package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"os/exec"
	"strings"
)

func main() {
	f, err := ioutil.TempFile("", "issue21317.go")
	if err != nil {
		log.Fatal(err)

The benefit of raising an exception over `return`ing a value will be more evident in the section about Dependencies and Security.

In this example, when the client requests an item by an ID that doesn't exist, raise an exception with a status code of `404`:

```Python hl_lines="11"