old_contents: from __future__ import unicode_literals
  
  from ..base import Resource
  
  
  class Customer(Resource):
      _resource_name = 'customers'
      _is_listable = False
      _is_parent_resource = True
  
      _as_is_fields = [
          'id', 'href', 'place_of_birth', 'meal_preference', 'meal_notes',
          'emergency_contacts', 'medical_notes', 'phone_numbers',
          'account_email', 'name', 'passport', 'address', 'nationality',
          'gender',
      ]
  
      _date_fields = ['date_of_birth', ]
  
      @property
      def _resource_collection_fields(self):
          from .booking import Booking
          return [
              ('bookings', Booking),
          ]
  
new_contents: from __future__ import unicode_literals
  
  from ..base import Resource
  
  
  class Customer(Resource):
      _resource_name = 'customers'
      _is_listable = False
      _is_parent_resource = True
  
      _as_is_fields = [
          'id', 'href', 'place_of_birth', 'meal_preference', 'meal_notes',
          'emergency_contacts', 'medical_details', 'phone_numbers',
          'account_email', 'name', 'passport', 'address', 'nationality',
          'gender',
      ]
  
      _date_fields = ['date_of_birth', ]
  
      @property
      def _resource_collection_fields(self):
          from .booking import Booking
          return [
              ('bookings', Booking),
          ]
  
subject: Replace customers.medical_notes with customers.medical_details