如何删除Django两个模型之间的许多关系

class Question(models.Model):
      q_title = models.CharField(max_length=500)
      q_user = models.ForeignKey(MyUser, null=False, blank=False)
      q_slug = models.SlugField(null=True, blank=True)
      q_category=  models.ManyToManyField('Categories',null=True,blank=True)

class Categories(models.Model):
    category = models.CharField(max_length=200)
class Question(models.Model):
      q_title = m