def _unpack_schema_additions(self, items):

        unpacked_items = []

        for item in items:
            if isinstance(item, SchemaAddition):
                unpacked_items.append(item.factory())
            else:
                unpacked_items.append(item)

        return unpacked_items
Unpack additions, since they may themselves be schemas.
dataset/ETHPy150Open enthought/pyface/pyface/tasks/action/task_action_manager_builder.py/TaskActionManagerBuilder._unpack_schema_additions