remove
fun CloudStorage.remove(key: CloudStorageKey, callback: (result: Result<Boolean>) -> Unit): CloudStorage
fun CloudStorage.remove(keys: Array<CloudStorageKey>, callback: (result: Result<Boolean>) -> Unit): CloudStorage
fun CloudStorage.remove(keys: Array<String>, callback: (result: Result<Boolean>) -> Unit): CloudStorage
fun CloudStorage.remove(key: String, key2: String, vararg otherKeys: String, callback: (result: Result<Boolean>) -> Unit): CloudStorage