text: from django.contrib import admin
  
  
  class FeeAdmin(admin.ModelAdmin):
      list_display = (
          'label', 'num_sessions', 'price_cents', 'active')
      search_fields = [
          'label', 'num_sessions', 'price_cents', 'active']
      ordering = ['num_sessions', 'price_cents', 'active']
  
      def get_readonly_fields(self, request, obj=None):
          if obj:
              return ['num_sessions', 'price_cents']
          else:
              return []
  
      def has_delete_permission(self, request, obj=None):
          return False
  