code: def _represent_undefined(self, data):
      
      raise RepresenterError(
          _format("Cannot represent an object: {0!A} of type: {1}; "
                  "yaml_representers: {2!A}, "
                  "yaml_multi_representers: {3!A}",
                  data, type(data), self.yaml_representers.keys(),
                  self.yaml_multi_representers.keys()))
docs: Raises flag for objects that cannot be represented