old_contents: from django.db import models
  
  
  class BitemporalModelBase(models.Model):
  
      id = models.IntegerField()
      row_id = models.AutoField(primary_key=True)
  
      valid_start_date = models.DateTimeField(auto_now_add=True)
      valid_end_date = models.DateTimeField(blank=True, null=True)
  
      txn_start_date = models.DateTimeField(auto_now_add=True)
      txn_end_date = models.DateTimeField(blank=True, null=True)
  
      class Meta:
          abstract = True
          unique_together = [
              ('id', 'start_date', 'end_date', 'txn_end_date'),
          ]
  
new_contents: from django.db import models
  
  
  class BitemporalModelBase(models.Model):
  
      id = models.IntegerField()
      row_id = models.AutoField(primary_key=True)
  
      valid_start_date = models.DateTimeField(auto_now_add=True)
      valid_end_date = models.DateTimeField(blank=True, null=True)
  
      txn_start_date = models.DateTimeField(auto_now_add=True)
      txn_end_date = models.DateTimeField(blank=True, null=True)
  
      class Meta:
          abstract = True
          unique_together = [
              ('id', 'valid_start_date', 'valid_end_date', 'txn_end_date'),
          ]
  
subject: Fix another typo