我有以下模型和序列化器，目标是序列化器运行时只有一个查询:模型:classAssignee(EmbeddedDocument):id=ObjectIdField(primary_key=True)assignee_email=EmailField(required=True)assignee_first_name=StringField(required=True)assignee_last_name=StringField()assignee_time=DateTimeField(required=True,default=datetime.datetime.utcnow)user=