content: import django.db.models.deletion
  from django.db import migrations, models
  
  
  def populate_denormalized_fields(apps, schema_editor):
      """
      Copy site ForeignKey values to the Termination GFK.
      """
      CircuitTermination = apps.get_model('circuits', 'CircuitTermination')
      db_alias = schema_editor.connection.alias
  
      terminations = CircuitTermination.objects.using(db_alias).filter(site__isnull=False).prefetch_related('site')
      for termination in terminations:
          termination._region_id = termination.site.region_id
          termination._site_group_id = termination.site.group_id
          termination._site_id = termination.site_id
          # Note: Location cannot be set prior to migration
  
      CircuitTermination.objects.using(db_alias).bulk_update(
          terminations,
          ['_region', '_site_group', '_site'],
          batch_size=100
      )
  
  
  class Migration(migrations.Migration):
      dependencies = [
          ('circuits', '0047_circuittermination__termination'),
      ]
  
      operations = [
          migrations.AddField(
              model_name='circuittermination',
              name='_location',
              field=models.ForeignKey(
                  blank=True,
                  null=True,
                  on_delete=django.db.models.deletion.CASCADE,
                  related_name='circuit_terminations',
                  to='dcim.location',
              ),
          ),
          migrations.AddField(
              model_name='circuittermination',
              name='_region',
              field=models.ForeignKey(
                  blank=True,
                  null=True,
                  on_delete=django.db.models.deletion.CASCADE,
                  related_name='circuit_terminations',
                  to='dcim.region',
              ),
          ),
          migrations.AddField(
              model_name='circuittermination',
              name='_site',
              field=models.ForeignKey(
                  blank=True,
                  null=True,
                  on_delete=django.db.models.deletion.CASCADE,
                  related_name='circuit_terminations',
                  to='dcim.site',
              ),
          ),
          migrations.AddField(
              model_name='circuittermination',
              name='_site_group',
              field=models.ForeignKey(
                  blank=True,
                  null=True,
                  on_delete=django.db.models.deletion.CASCADE,
                  related_name='circuit_terminations',
                  to='dcim.sitegroup',
              ),
          ),
          # Populate denormalized FK values
          migrations.RunPython(code=populate_denormalized_fields, reverse_code=migrations.RunPython.noop),
          # Delete the site ForeignKey
          migrations.RemoveField(
              model_name='circuittermination',
              name='site',
          ),
          migrations.RenameField(
              model_name='circuittermination',
              old_name='provider_network',
              new_name='_provider_network',
          ),
      ]
  
  
  def oc_circuittermination_remove_fields(objectchange, reverting):
      for data in (objectchange.prechange_data, objectchange.postchange_data):
          if data is not None:
              data.pop('site', None)
              data.pop('provider_network', None)
  
  
  objectchange_migrators = {
      'circuits.circuittermination': oc_circuittermination_remove_fields,
  }
  