Worked on the plone/plone.restapi repository to enhance the reliability of its serialization layer by addressing a critical bug in the RelationListFieldSerializer. Focused on backend and API development using Python, the work involved correcting the handling of mutable default arguments in the get_value method. By replacing the mutable list default with None and ensuring an empty list is returned when values are missing or defaults are unset, the update eliminated unintended side effects and improved the predictability of API responses. This targeted bug fix contributed to greater stability for downstream consumers relying on the plone.restapi’s data serialization logic.