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: cluster_user_attribute.go
    path of file: ./repos/rancher/pkg/controllers/managementuser/clusterauthtoken
    
    the code of the file until where you have to start completion: package clusterauthtoken

import (
	clusterv3 "github.com/rancher/rancher/pkg/generated/norman/cluster.cattle.io/v3"
	managementv3 "github.com/rancher/rancher/pkg/generated/norman/management.cattle.io/v3"
	"k8s.io/apimachinery/pkg/runtime"
)

type clusterUserAttributeHandler struct {
	userAttribute       managementv3.UserAttributeInterface
	userAttributeLister managementv3.UserAttributeLister
}

// Sync clusterUserAttributes and userAttributes
func (h *clusterUserAttributeHandler) Sync(key string, clusterUserAttribute *clusterv3.ClusterUserAttribute) (runtime.
    
func (h *clusterUserAttributeHandler) Sync(key string, clusterUserAttribute *clusterv3.ClusterUserAttribute) (runtime.Object, error) {
	if clusterUserAttribute == nil || clusterUserAttribute.DeletionTimestamp != nil {
		return nil, nil
	}

	if !clusterUserAttribute.NeedsRefresh {
		return nil, nil
	}

	userAttribute, err := h.userAttributeLister.Get("", clusterUserAttribute.Name)
	if err != nil {
		return nil, err
	}

	if userAttribute.NeedsRefresh {
		return nil, nil
	}
	if userAttribute.LastRefresh != clusterUserAttribute.LastRefresh {
		return nil, nil
	}

	userAttribute.NeedsRefresh = true
	_, err = h.userAttribute.Update(userAttribute)
	return nil, err
}