def METHOD_NAME(self):
    self.workflow.do_engine_steps()
    user_task = self.workflow.get_ready_user_tasks()[0]
    def f(n):
        return n + 1
    user_task.data = { 'f': f }
    task_id = str(user_task.id)
    dct = self.serializer.workflow_to_dict(self.workflow)
    self.assertNotIn('f', dct['tasks'][task_id]['data'])