Python 动态修改django Rest Framework中的字段

好，我有两个类，一个是Book，另一个是Category.Book和Category由一个名为Category的外键链接，该外键是一个Book字段. 请参阅代码

class Category(models.Model):
    class Meta:
        verbose_name_plural = "Categories"

    category = models.CharField(max_length=20)

    def __str__(self):
        return self.category


class Book(models.Model):
    book_title = models.CharField(max_length=20)
    category = models.ForeignKey(Category, on_delete=models.CASCADE)

    def __str__(self):
        return self.book_title

下面是序列化程序类

class DynamicFieldsModelSerializer(serializers.ModelSerializer):
    """
    A ModelSerializer that takes an additional `fields` argument that
    controls which fields should be displayed.
    """

    def __init__(self, *args, **kwargs):
        # Don't pass the 'fields' arg up to the superclass
        fields = kwargs.pop('fields', None)

        # Instantiate the superclass normally
        super().__init__(*args, **kwargs)

        if fields is not None:
            # Drop any fields that are not specified in the `fields` argument.
            allowed = set(fields)
            existing = set(self.fields)
            for field_name in existing - allowed:
                self.fields.pop(field_name)


class CategorySerializer(DynamicFieldsModelSerializer):
    class Meta:
        model = Category
        # only show the category field 
        fields = ['category']

class BookSerializer(serializers.ModelSerializer):
    # this will show the category data which is related to this Book
    category = CategorySerializer()
    class Meta: 
        model = Book
        fields = '__all__'

现在我希望，当我使用@api_view获取图书的数据时，我应该只获得类别名称，这是完全没有问题的，但当我想要查看Category的数据时，我希望看到所有字段.但它什么也没显示出来. @api_view代码

@api_view(['GET'])
def getBooks(request):
    books = Book.objects.all()
    serilized_data = BookSerializer(books,many=True)
    return Response({'status': 200, 'payload': serilized_data.data})


# it is now only show the category as only category field is passed in CategorySerilizer
@api_view(['GET'])
def getCategory(request):
    category = Category.objects.all()
    serilized_data = CategorySerializer(category,fields = ('__all__'),many=True)
    return Response({'status': 200, 'payload': serilized_data.data})

而getCategory的输出是

{
    "status": 200,
    "payload": [
        {},
        {}
    ]
}

还有一件事需要注意的是，我的数据库中只有两个类别，它也通过{}，{}显示