new_contents: from django.db import migrations
  from django.db.models import Case, Value, When
  
  
  def backfill_has_matches(apps, schema_editor):
      YaraResult = apps.get_model('yara', 'YaraResult')
      YaraResult.objects.filter(has_matches=None).update(
          has_matches=Case(
              When(matches='[]', then=Value(False)),
              default=Value(True)
          )
      )
  
  
  class Migration(migrations.Migration):
  
      dependencies = [
          ('yara', '0002_auto_20191009_1239'),
      ]
  
      operations = [
          migrations.RunPython(backfill_has_matches),
      ]
  
subject: Add data migration to backfill YaraResult.has_matches