old_contents: from django.contrib import admin
  from django.utils.translation import ugettext_lazy as _
  
  from .models import Room, ScheduleItem
  
  
  @admin.register(ScheduleItem)
  class ScheduleItemAdmin(admin.ModelAdmin):
      list_display = ("conference", "start", "end", "type", "title", "submission")
      ordering = ("conference", "start")
      fieldsets = (
          (
              _("Event"),
              {
                  "fields": (
                      "conference",
                      "type",
                      "title",
                      "image",
                      "description",
                      "submission",
                      "additional_speakers",
                  )
              },
          ),
          (_("Schedule"), {"fields": ("start", "end", "rooms")}),
      )
      autocomplete_fields = ("submission",)
      filter_horizontal = ("rooms", "additional_speakers")
  
  
  @admin.register(Room)
  class RoomAdmin(admin.ModelAdmin):
      list_display = ("name", "conference")
      list_filter = ("conference",)
  
new_contents: from django.contrib import admin
  from django.utils.translation import ugettext_lazy as _
  
  from .models import Room, ScheduleItem
  
  
  @admin.register(ScheduleItem)
  class ScheduleItemAdmin(admin.ModelAdmin):
      list_display = ("title", "conference", "start", "end", "type", "submission")
      ordering = ("conference", "start")
      fieldsets = (
          (
              _("Event"),
              {
                  "fields": (
                      "conference",
                      "type",
                      "title",
                      "image",
                      "description",
                      "submission",
                      "additional_speakers",
                  )
              },
          ),
          (_("Schedule"), {"fields": ("start", "end", "rooms")}),
      )
      autocomplete_fields = ("submission",)
      filter_horizontal = ("rooms", "additional_speakers")
  
  
  @admin.register(Room)
  class RoomAdmin(admin.ModelAdmin):
      list_display = ("name", "conference")
      list_filter = ("conference",)
  
subject: Improve admin for schedule