Fix 3.9

Change-Id: Iee02352ca21fa66da9b097d4dfa9454b67609e79

Author: MarkDaoust

google/generativeai/types/image_types/_image_types.py

@@ -44,7 +44,7 @@
 def _pil_to_blob(image: PIL.Image.Image) -> protos.Blob:
     # If the image is a local file, return a file-based blob without any modification.
     # Otherwise, return a lossless WebP blob (same quality with optimized size).
-    def file_blob(image: PIL.Image.Image) -> protos.Blob | None:
+    def file_blob(image: PIL.Image.Image) -> Union[protos.Blob, None]:
         if not isinstance(image, PIL.ImageFile.ImageFile) or image.filename is None:
             return None
         filename = str(image.filename)