code: def _get_field(instance, field):
      
      
      value = getattr(instance, field)
      if hasattr(value, 'raw'):
          value = value.raw
      return value
docs: This is here to support ``MarkupField``. It's a little ugly to
      have that support baked-in; other option would be to have a
      generic way (via setting?) to override how attribute values are
      fetched from content model instances.