old_contents: from django.contrib import admin
  
  from .models import AudienceLevel, Conference, Deadline, Duration, TicketFare, Topic
  
  
  class DeadlineInline(admin.TabularInline):
      model = Deadline
  
  
  class DurationInline(admin.StackedInline):
      model = Duration
      filter_horizontal = ("allowed_submission_types",)
  
  
  @admin.register(Conference)
  class ConferenceAdmin(admin.ModelAdmin):
      readonly_fields = ("created", "modified")
      filter_horizontal = ("topics", "languages", "audience_levels", "submission_types")
      fieldsets = (
          (
              "Details",
              {
                  "fields": (
                      "name",
                      "code",
                      "timezone",
                      "latitude",
                      "longitude",
                      "map_link",
                  )
              },
          ),
          (
              "Conference",
              {
                  "fields": (
                      ("start", "end"),
                      "submission_types",
                      "topics",
                      "audience_levels",
                      "languages",
                  )
              },
          ),
      )
      inlines = [DeadlineInline, DurationInline]
  
  
  @admin.register(Topic)
  class TopicAdmin(admin.ModelAdmin):
      pass
  
  
  @admin.register(AudienceLevel)
  class AudienceLevelAdmin(admin.ModelAdmin):
      pass
  
  
  @admin.register(TicketFare)
  class TicketFareAdmin(admin.ModelAdmin):
      list_display = ("conference", "name")
      list_filter = ("conference", "questions")
  
      fieldsets = (
          ("Info", {"fields": ("conference", "name", "code", "price", "description")}),
          ("Deadline", {"fields": ("start", "end")}),
          ("TicketQuestion", {"fields": ("questions",)}),
      )
  
new_contents: from django.contrib import admin
  
  from .models import AudienceLevel, Conference, Deadline, Duration, TicketFare, Topic
  
  
  class DeadlineInline(admin.TabularInline):
      model = Deadline
  
  
  class DurationInline(admin.StackedInline):
      model = Duration
      filter_horizontal = ("allowed_submission_types",)
  
  
  @admin.register(Conference)
  class ConferenceAdmin(admin.ModelAdmin):
      readonly_fields = ("created", "modified")
      filter_horizontal = ("topics", "languages", "audience_levels", "submission_types")
      fieldsets = (
          (
              "Details",
              {
                  "fields": (
                      "name",
                      "code",
                      "timezone",
                      "latitude",
                      "longitude",
                      "map_link",
                  )
              },
          ),
          (
              "Conference",
              {
                  "fields": (
                      ("start", "end"),
                      "submission_types",
                      "topics",
                      "audience_levels",
                      "languages",
                  )
              },
          ),
      )
      inlines = [DeadlineInline, DurationInline]
  
  
  @admin.register(Topic)
  class TopicAdmin(admin.ModelAdmin):
      pass
  
  
  @admin.register(AudienceLevel)
  class AudienceLevelAdmin(admin.ModelAdmin):
      pass
  
  
  @admin.register(TicketFare)
  class TicketFareAdmin(admin.ModelAdmin):
      list_display = ("conference", "name")
      list_filter = ("conference", "questions")
      filter_horizontal = ("questions",)
  
      fieldsets = (
          ("Info", {"fields": ("conference", "name", "code", "price", "description")}),
          ("Deadline", {"fields": ("start", "end")}),
          ("TicketQuestion", {"fields": ("questions",)}),
      )
  
subject: Use filter_horizontal for the ticket fare questions