old_contents: from django.db import models
  
  # Create your models here.
  
new_contents: from django.db import models
  
  class Bill(models.Model):
  
      bill_date = models.DateField(auto_now_add=True)
      line = models.ForeignKey('BillLine')
  
  class BillLine(models.Model):
  
       SERVICES_CHOICES = (
              (FT, 'Full Time'),
              (PT, 'Part Time'),
              (MD, 'Mid Time'),
              )
  
      service = models.CharField(max_length=2, choices=SERVICES_CHOICES, 
                                 default=Full Time)
      quantity = models.SmallIntegerField()
  
  
subject: create Bill and BillLine object