我可以在unicode返回中使用外键吗？

Question

我有以下的课程：配料，配方和沉淀物。。。

class Ingredient(models.Model):
    name = models.CharField(max_length=30, primary_key=True)
    qty_on_stock = models.IntegerField()

    def __unicode__(self):
        return self.name

class Recipe(models.Model):
    name = models.CharField(max_length=30, primary_key=True)
    comments = models.TextField(blank=True)
    ingredient = models.ManyToManyField(Ingredient)

    def __unicode__(self):
        return self.name

class RecipeContent(models.Model):
    recipe = models.ForeignKey(Recipe)
    ingredients = models.ForeignKey(Ingredient)
    qty_used = models.IntegerField()

但对于RecipeContent中的unicode，我想使用此RecipeContent所属的配方名称。。。有办法吗？