code: def forwards(self, orm):
      # Rename 'url' field to 'source_url' in Item
      db.rename_column("timeside_items", "url", "source_url")
      # Rename 'file' field to 'source_file' in Item
      db.rename_column("timeside_items", "file", "source_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 1 for calling the Migration obj's underlying member method code with example usage: obj.forwards(orm) without return types