Django投票模型选择，如何更改我的模型？

from django.db import models

class Question(models.Model):
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')

class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

class Question(models.Model):
    QUESTION_TYPES = (
        ('choice', '选择题'),
        ('fill_in', '填空题'),
    )
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')
    question_type = models.CharField(max_length=10, choices=QUESTION_TYPES)

class Question(models.Model):
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')

class Choice(models.Model):
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

class QuestionChoice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice = models.ForeignKey(Choice, on_delete=models.CASCADE)

python manage.py makemigrations
python manage.py migrate