在django admin中过滤外键字段

I have these models:

我有这些模型：

class Entity(models.Model):
       name=models.CharField(max_length=100)

class Theme(models.Model):
   name=models.CharField(max_length=100)
   entity=models.OneToOneField(Entity)

class Company(models.Model):
    name=models.CharField(max_length=100)
    theme=models.OneToOneField(Theme,null=True,blank=True)
class Entity(