text: """
  copied and amended from https://github.com/furious-luke/django-address
  """
  
  from django.contrib import admin
  from django.contrib.admin import SimpleListFilter
  from .models import *
  
  class UnidentifiedListFilter(SimpleListFilter):
      title = 'unidentified'
      parameter_name = 'unidentified'
  
      def lookups(self, request, model_admin):
          return (('unidentified', 'unidentified'),)
  
      def queryset(self, request, queryset):
          if self.value() == 'unidentified':
              return queryset.filter(locality=None)
  
  @admin.register(Country)
  class CountryAdmin(admin.ModelAdmin):
      search_fields = ('name', 'code')
  
  @admin.register(State)
  class StateAdmin(admin.ModelAdmin):
      search_fields = ('name', 'code')
  
  @admin.register(Locality)
  class LocalityAdmin(admin.ModelAdmin):
      search_fields = ('name',)
  
  @admin.register(Address)
  class AddressAdmin(admin.ModelAdmin):
      search_fields = ('name',)
      list_filter = (UnidentifiedListFilter,)
  