Clarify (de)serialization of custom data types in Python

'Exporting' doesn't exist in Python. The use of the official and established term 'class method' clarifies how the methods for (de)serialization have to be defined.

Author: jparta

articles/azure-functions/durable/durable-functions-serialization-and-persistence.md

@@ -155,7 +155,7 @@ For full customization of the serialization/deserialization pipeline, consider h
 
 It's recommended to use type annotations to ensure Durable Functions serializes and deserializes your data correctly. While many built-in types are handled automatically, some built-in data types require type annotations to preserve the type during deserialization.
 
-For custom data types, you must define the JSON serialization and deserialization of a data type by exporting a static `to_json` and `from_json` method from your class.
+For custom data types, you make JSON serialization and deserialization possible by defining class methods `to_json` and `from_json` on your data type class.
 
 # [Java](#tab/java)