如何根据外表中的值为django TabularInline动态设置max_num？

考虑以下数据模型:

class Model(models.Model):
    """A specific model of managed network switch. """
    name = models.CharField(max_length=20)
    port_count = models.IntegerField()

class Switch(models.Model):
    """A deployed instance of a managed network switch."""
    model = models.ForeignKey(Model)
    name = models.CharField(max_length=14)

class Port(models.Model):
    """A port on a deployed instance of a managed network switch."""
    switch = models.ForeignKey(Switch)
    number = models.IntegerField()
    ip_address = models.GenericIPAddressField(
        protocol='IPv4', verbose_name='IP address')
    netmask = models.GenericIPAddressField(protocol='IPv4')
    vlan = models.IntegerField(verbose_name='VLAN')

我想要我的管理页面,以便在Switch下内联端口.所以我有:

class PortInLineAdmin(admin.TabularInline):
    model = Port
    extra = 8
    max_num = 48

class SwitchAdmin(admin.ModelAdmin):
    inlines = [PortInLineAdmin]

这非常接近我想要实现的目标.但是,我真正想要的是PortInLineAdmin.max_num在运行时将动态设置为 Model.port_count我正在编辑的交换机而不是在48处进行硬编码,如上所示.我如何实现这一目标？