Add missing import for typing Optional

asyncua/common/structures.py

@@ -223,7 +223,7 @@ THIS FILE IS AUTOGENERATED, DO NOT EDIT!!!
 from datetime import datetime, timezone
 import uuid
 from dataclasses import dataclass, field
-from typing import List, Union
+from typing import List, Union, Optional
 from enum import IntEnum
 
 from asyncua import ua