Django admin：如何根据另一个选择框限制相关的选择框值

class Products(models.Model):
    name = models.CharField(max_length=50)

    leve1 = models.ForeignKey( Level1 )
    leve2 = models.ForeignKey( Level2 )
    leve3 = models.ForeignKey( Level3 )
    leve4 = models.ForeignKey( Level4 )



class Level1(models.Model):
    name = models.CharField(max_length=50)

class Level2(models.Model):
    name = models.CharField(max_length=50)
    leve1 = models.ForeignKey( Level1 )

class Level3(models.Model):
    name = models.CharField(max_length=50)
    leve2 = models.ForeignKey( Level2 )

class Level4(models.Model):
    name = models.CharField(max_length=50)
    leve3 = models.ForeignKey( Level3 )
class Products(models.Model):
    name = models