old_contents: from django.contrib import admin
  from .models import Facility, Schedule, OpenTime, Category
  
  class OpenTimeInline(admin.TabularInline):
      model = OpenTime
      fk_name = 'schedule'
      max_num = 7
  
  class OpenTimeAdmin(admin.ModelAdmin):
      pass
  
  class FacilityAdmin(admin.ModelAdmin):
      model = Facility
      list_display = ['name', 'location' ]
      list_filter = ['facility_category', ]
      fieldsets = (
          (None, {
               'fields': ('name', 'facility_category',
                         ('location', 'on_campus'),
                         'main_schedule', 'special_schedules',
                         'owners'),
                 }),
      )
  
  class ScheduleAdmin(admin.ModelAdmin):
      inlines = [OpenTimeInline, ]
      fieldsets = (
          (None, {
               'fields': ('name',
                         ('valid_start', 'valid_end'),)
                 }),
      )
  
  class CategoryAdmin(admin.ModelAdmin):
      pass
  
  admin.site.register(Facility, FacilityAdmin)
  admin.site.register(Schedule, ScheduleAdmin)
  #admin.site.register(OpenTime, OpenTimeAdmin)
  admin.site.register(Category, CategoryAdmin)
  
new_contents: from django.contrib import admin
  from .models import Facility, Schedule, OpenTime, Category
  
  class OpenTimeInline(admin.TabularInline):
      model = OpenTime
      fk_name = 'schedule'
      max_num = 7
  
  class OpenTimeAdmin(admin.ModelAdmin):
      pass
  
  class FacilityAdmin(admin.ModelAdmin):
      model = Facility
      list_display = ['name', 'location' ]
      list_filter = ['facility_category', ]
      fieldsets = (
          (None, {
               'fields': ('name', 'facility_category',
                          ('location', 'on_campus'),
                          'main_schedule', 'special_schedules', ),
          }),
          ('Advanced', {
               'fields': ('owners', ),
               'classes': ('collapse', ),
          }),
      )
  
  class ScheduleAdmin(admin.ModelAdmin):
      inlines = [OpenTimeInline, ]
      fieldsets = (
          (None, {
               'fields': ('name',
                         ('valid_start', 'valid_end'),)
                 }),
      )
  
  class CategoryAdmin(admin.ModelAdmin):
      pass
  
  admin.site.register(Facility, FacilityAdmin)
  admin.site.register(Schedule, ScheduleAdmin)
  #admin.site.register(OpenTime, OpenTimeAdmin)
  admin.site.register(Category, CategoryAdmin)
  
subject: move 'owner' field to collapsed 'advanced' section for facility