<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def serialize(self, submit=None):
 """Serialize each form field to a Payload container. :param Submit submit: Optional `Submit` to click, if form includes multiple submits :return: Payload instance """

        include_fields = prepare_fields(self.fields, self.submit_fields, submit)
        return Payload.from_fields(include_fields)