You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: admission.go
    path of file: ./repos/kubernetes/plugin/pkg/admission/network/denyserviceexternalips
    
    the code of the file until where you have to start completion: /*
Copyright 2020 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package
    
func (plug *externalIPsDenierPlugin) Validate(ctx context.Context, attr admission.Attributes, o admission.ObjectInterfaces) error {
	if attr.GetResource().GroupResource() != core.Resource("services") {
		return nil
	}

	if len(attr.GetSubresource()) != 0 {
		return nil
	}

	// if we can't convert then we don't handle this object so just return
	newSvc, ok := attr.GetObject().(*core.Service)
	if !ok {
		klog.V(3).Infof("Expected Service resource, got: %v", attr.GetKind())
		return errors.NewInternalError(fmt.Errorf("Expected Service resource, got: %v", attr.GetKind()))
	}

	var oldSvc *core.Service
	if old := attr.GetOldObject(); old != nil {
		tmp, ok := old.(*core.Service)
		if !ok {
			klog.V(3).Infof("Expected Service resource, got: %v", attr.GetKind())
			return errors.NewInternalError(fmt.Errorf("Expected Service resource, got: %v", attr.GetKind()))
		}
		oldSvc = tmp
	}

	if isSubset(newSvc, oldSvc) {
		return nil
	}

	klog.V(4).Infof("Denying new use of ExternalIPs on Service %s/%s", newSvc.Namespace, newSvc.Name)
	return admission.NewForbidden(attr, fmt.Errorf("Use of external IPs is denied by admission control"))
}