```
var _ generic.StorageDecorator = StorageWithCacher
// Creates a cacher based given storageConfig.
func StorageWithCacher(
copier runtime.ObjectCopier,
// 配置 etcd api version, server addr 等参数.
storageConfig *storagebackend.Config,
capacity int,
objectType runtime.Object,
resourcePrefix string,
keyFunc func(obj runtime.Object) (string, error),
newListFunc func() runtime.Object,
getAttrsFunc storage.AttrFunc,
triggerFunc storage.TriggerPublisherFunc) (storage.Interface, factory.DestroyFunc) {
// 读取配置 etcd 的配置，如 API 版本，tls 认证等信息，创建 etcd 连接以及 Storage Interface
s, d := generic.NewRawStorage(storageConfig)
// TODO: we would change this later to make storage always have cacher and hide low level KV layer inside.
// Currently it has two layers of same storage interface -- cacher and low level kv.
cacherConfig := storage.CacherConfig{
CacheCapacity: capacity,
Storage: s,
Versioner: etcdstorage.APIObjectVersioner{},
Copier: copier,
Type: objectType,
ResourcePrefix: resourcePrefix,
KeyFunc: keyFunc,
NewListFunc: newListFunc,
GetAttrsFunc: getAttrsFunc,
TriggerPublisherFunc: triggerFunc,
Codec: storageConfig.Codec,
}
cacher := storage.NewCacherFromConfig(cacherConfig)
destroyFunc := func() {
cacher.Stop()
d()
}
return cacher, destroyFunc
}
...
package generic
type StorageDecorator func(
copier runtime.ObjectCopier,
config *storagebackend.Config,
capacity int,
objectType runtime.Object,
resourcePrefix string,
keyFunc func(obj runtime.Object) (string, error),
newListFunc func() runtime.Object,
getAttrsFunc storage.AttrFunc,
trigger storage.TriggerPublisherFunc) (storage.Interface, factory.DestroyFunc)
```
提问：
StorageWithCacher 这个函数，返回两个值，这个 ```var _ generic.StorageDecorator``` 中下划线```_```是什么意思， 它并不是``` _ , xxx := ```
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