fix: 使用Union替代类型注解中的管道符号，使python3.9版本不报错

app/domain/image_models.py

@@ -1,23 +1,24 @@
+from typing import Union
+
+
 class ImageMetadata:
-    def __init__(self, width: int, height: int, filename: str, size: int, url: str, delete_url: str | None = None):
+    def __init__(self, width: int, height: int, filename: str, size: int, url: str, delete_url: Union[str, None] = None):
         self.width = width
         self.height = height
         self.filename = filename
         self.size = size
         self.url = url
         self.delete_url = delete_url
-    
-    
+
+
 class UploadResponse:
     def __init__(self, success: bool, code: str, message: str, data: ImageMetadata):
         self.success = success
         self.code = code
         self.message = message
         self.data = data
-    
-    
+
+
 class ImageUploader:
     def upload(self, file: bytes, filename: str) -> UploadResponse:
         raise NotImplementedError
-    
-