code: def backwards(self, orm):
      # Rename 'source_url' field back to 'url' in Item
      db.rename_column("timeside_items", "source_url", "url")
      # Rename 'source_file' field back to 'file' in Item
      db.rename_column("timeside_items", "source_file", "file")
  
imports: from south.utils import datetime_utils
  from south.db import db
  from south.v2 import SchemaMigration
  from django.db import models
label_desc: Use image node_id 2 for calling the Migration obj's underlying member method code with example usage: obj.backwards(orm) without return types