old_contents: from django.contrib import admin
  from .models import VehicleType, Vehicle, VehicleJourney, Livery, JourneyCode
  
  
  def copy_livery(modeladmin, request, queryset):
      livery = Livery.objects.filter(vehicle__in=queryset).first()
      queryset.update(livery=livery)
  
  
  def copy_type(modeladmin, request, queryset):
      vehicle_type = VehicleType.objects.filter(vehicle__in=queryset).first()
      queryset.update(vehicle_type=vehicle_type)
  
  
  class VehicleTypeAdmin(admin.ModelAdmin):
      search_fields = ('name',)
      list_display = ('name', 'double_decker', 'coach')
      list_editable = list_display[1:]
  
  
  class VehicleAdmin(admin.ModelAdmin):
      list_display = ('code', 'fleet_number', 'reg', 'operator', 'vehicle_type', 'livery', 'colours', 'notes')
      list_filter = (
          ('operator', admin.RelatedOnlyFieldListFilter),
          ('source', admin.RelatedOnlyFieldListFilter),
          'vehicle_type',
      )
      list_select_related = ['operator', 'vehicle_type']
      list_editable = ('fleet_number', 'reg', 'operator', 'vehicle_type', 'livery', 'colours', 'notes')
      search_fields = ('code', 'fleet_number', 'reg')
      raw_id_fields = ('operator',)
      autocomplete_fields = ('vehicle_type',)
      ordering = ('-id',)
      actions = (copy_livery, copy_type)
  
  
  class VehicleJourneyAdmin(admin.ModelAdmin):
      list_display = ('datetime', 'vehicle', 'service', 'route_name', 'code', 'destination')
      list_select_related = ('vehicle', 'service')
      raw_id_fields = ('vehicle', 'service')
      list_filter = (
          ('service', admin.BooleanFieldListFilter),
          ('source', admin.RelatedOnlyFieldListFilter),
          'vehicle__operator',
      )
      ordering = ('-id',)
  
  
  class JourneyCodeAdmin(admin.ModelAdmin):
      list_display = ['code', 'service', 'destination']
      list_select_related = ['service']
      raw_id_fields = ['service']
  
  
  class LiveryAdmin(admin.ModelAdmin):
      list_display = ['name', 'preview']
  
  
  admin.site.register(VehicleType, VehicleTypeAdmin)
  admin.site.register(Vehicle, VehicleAdmin)
  admin.site.register(VehicleJourney, VehicleJourneyAdmin)
  admin.site.register(JourneyCode, JourneyCodeAdmin)
  admin.site.register(Livery, LiveryAdmin)
  
new_contents: from django.contrib import admin
  from .models import VehicleType, VehicleFeature, Vehicle, VehicleJourney, Livery, JourneyCode
  
  
  def copy_livery(modeladmin, request, queryset):
      livery = Livery.objects.filter(vehicle__in=queryset).first()
      queryset.update(livery=livery)
  
  
  def copy_type(modeladmin, request, queryset):
      vehicle_type = VehicleType.objects.filter(vehicle__in=queryset).first()
      queryset.update(vehicle_type=vehicle_type)
  
  
  class VehicleTypeAdmin(admin.ModelAdmin):
      search_fields = ('name',)
      list_display = ('name', 'double_decker', 'coach')
      list_editable = list_display[1:]
  
  
  class VehicleAdmin(admin.ModelAdmin):
      list_display = ('code', 'fleet_number', 'reg', 'operator', 'vehicle_type', 'livery', 'colours', 'notes')
      list_filter = (
          ('operator', admin.RelatedOnlyFieldListFilter),
          ('source', admin.RelatedOnlyFieldListFilter),
          'vehicle_type',
      )
      list_select_related = ['operator', 'vehicle_type']
      list_editable = ('fleet_number', 'reg', 'operator', 'vehicle_type', 'livery', 'colours', 'notes')
      search_fields = ('code', 'fleet_number', 'reg')
      raw_id_fields = ('operator',)
      autocomplete_fields = ('vehicle_type',)
      ordering = ('-id',)
      actions = (copy_livery, copy_type)
  
  
  class VehicleJourneyAdmin(admin.ModelAdmin):
      list_display = ('datetime', 'vehicle', 'service', 'route_name', 'code', 'destination')
      list_select_related = ('vehicle', 'service')
      raw_id_fields = ('vehicle', 'service')
      list_filter = (
          ('service', admin.BooleanFieldListFilter),
          ('source', admin.RelatedOnlyFieldListFilter),
          'vehicle__operator',
      )
      ordering = ('-id',)
  
  
  class JourneyCodeAdmin(admin.ModelAdmin):
      list_display = ['code', 'service', 'destination']
      list_select_related = ['service']
      raw_id_fields = ['service']
  
  
  class LiveryAdmin(admin.ModelAdmin):
      list_display = ['name', 'preview']
  
  
  admin.site.register(VehicleType, VehicleTypeAdmin)
  admin.site.register(VehicleFeature)
  admin.site.register(Vehicle, VehicleAdmin)
  admin.site.register(VehicleJourney, VehicleJourneyAdmin)
  admin.site.register(JourneyCode, JourneyCodeAdmin)
  admin.site.register(Livery, LiveryAdmin)
  
subject: Add vehicle feature admin