old_contents: from django.contrib.admin import ModelAdmin, StackedInline, register
  
  from .models import Place, Country, CountryHealth, CountryDetail
  
  @register(Place)
  class PlaceAdmin(ModelAdmin):
      list_display = ('name', 'country', 'rank', 'pop', 'timezone')
      search_fields = ('name',)
  
  class HealthInline(StackedInline):
      model = CountryHealth
  
  class DetailInline(StackedInline):
      model = CountryDetail
  
  @register(Country)
  class CountryAdmin(ModelAdmin):
      list_display = ('name', 'iso2', 'iso3')
      list_filter = ('region', 'subregion')
      search_fields = ('name', 'iso2', 'iso3', 'detail__name_short',
                       'detail__name_abbr')
  
      inlines = [HealthInline, DetailInline]
  
  @register(CountryDetail)
  class CountryDetailAdmin(ModelAdmin):
      list_display = ('__str__', 'name_short', 'name_abbr',
                      'rank', 'pop', 'continent')
      list_filter = ('continent', 'mapcolor')
      search_fields = ('country__name', 'name_short', 'name_abbr',)
  
new_contents: from django.contrib.admin import ModelAdmin, StackedInline, register
  
  from .models import Place, Country, CountryHealth, CountryDetail
  
  @register(Place)
  class PlaceAdmin(ModelAdmin):
      list_display = ('name', 'country', 'rank', 'pop', 'timezone')
      search_fields = ('name',)
  
  class HealthInline(StackedInline):
      model = CountryHealth
  
  class DetailInline(StackedInline):
      model = CountryDetail
  
  @register(Country)
  class CountryAdmin(ModelAdmin):
      list_display = ('name', 'iso2', 'iso3')
      list_filter = ('region', 'subregion')
      search_fields = ('name', 'iso2', 'iso3', 'detail__name_short',
                       'detail__name_abbr')
  
      inlines = [HealthInline, DetailInline]
  
  @register(CountryHealth)
  class CountryHealthAdmin(ModelAdmin):
      list_display = ('country',)
  
  @register(CountryDetail)
  class CountryDetailAdmin(ModelAdmin):
      list_display = ('__str__', 'name_short', 'name_abbr',
                      'rank', 'pop', 'continent')
      list_filter = ('continent', 'mapcolor')
      search_fields = ('country__name', 'name_short', 'name_abbr',)
  
subject: Add admin interface