django admin显示多对多字段ManyToManyField

from .models import *
class BookAdmin(admin.ModelAdmin):
    list_display = ["title","作者"]
    def 作者(self, obj):
             return [bt.name for bt in obj.authors.all()]
    filter_horizontal = (‘authors‘,)  

admin.site.register(Book,BookAdmin)

class Book(models.Model):
    title = models.CharField(max_length=32)
    authors = models.ManyToManyField("Author")
    def __str__(self):
        return self.title

class Author(models.Model):
    name = models.CharField(max_length=32)

    def __str__(self):
        return self.name