Make ApiContentInfo.publication_date optional as it is optionally returned by Amazon.

YPCrumble · YPCrumble · commit 167ccb35ed69 · 2022-09-13T16:24:27.000-04:00
diff --git a/amazon_paapi/models/item_result.py b/amazon_paapi/models/item_result.py
@@ -86,7 +86,7 @@ class ApiClassifications(models.Classifications):
 class ApiContentInfo(models.ContentInfo):
     edition: ApiSingleStringValuedAttribute
     languages: ApiMultiValuedAttributeType
-    publication_date: ApiSingleStringValuedAttribute
+    publication_date: Optional[ApiSingleStringValuedAttribute]
 
 
 class ApiContentRating(models.ContentRating):
