docs: def GetRDFValueType(self):
      """Returns this attribute's RDFValue class."""
      result = self.attribute_type
      for field_name in self.field_names:
        # Support the new semantic protobufs.
        try:
          result = result.type_infos.get(field_name).type
        except AttributeError:
          raise AttributeError("Invalid attribute %s" % field_name)
  
      return result