自定义admin组件

1.admin 参数配置

2.注册

单例模式：admin.site=AdminSite(): 单例对象

# 此处是部分源码

class AdminSite(object):
    def __init__(self, name='admin'):
        self._registry = {}
    def register(self, model, admin_class=None, **options):
        if not admin_class:
    admin_class = ModelAdmin
    self._registry[model] = admin_class(model, self) 
    # {Book:ModelAdmin(Book)}