code: def upload_to(field_path, default):
      
      from yacms.conf import settings
      for k, v in settings.UPLOAD_TO_HANDLERS.items():
          if k.lower() == field_path.lower():
              return import_dotted_path(v)
      return default
docs: Used as the ``upload_to`` arg for file fields - allows for custom
      handlers to be implemented on a per field basis defined by the
      ``UPLOAD_TO_HANDLERS`` setting.