Django的NotImplementedError：没有实现annotate（）+ distinct（fields）

There are 2 simple models:

有2个简单的模型:

class Question(TimeStampedModel):
    text = models.CharField(max_length=40)

class Answer(TimeStampedModel):
    question = models.ForeignKey(Question, related_name='answers')
    is_agreed = models.BooleanField()
    author = models.ForeingKey(User, related_name='answers')
class