Merge pull request #3650 from silviogutierrez/master

Documentation fix for list serializers.

docs/api-guide/serializers.md

@@ -800,6 +800,10 @@ Here's an example of how you might choose to implement multiple updates:
             return ret
 
     class BookSerializer(serializers.Serializer):
+        # We need to identify elements in the list using their primary key,
+        # so use a writable field here, rather than the default which would be read-only.
+        id = serializers.IntegerField()
+
         ...
         class Meta:
             list_serializer_class = BookListSerializer