code: def add_untagged(self, *responses: 'Response') -> None:
          
          for resp in responses:
              try:
                  merge_key = resp.merge_key
              except TypeError:
                  self._untagged.append(resp)
              else:
                  key = (type(resp), merge_key)
                  try:
                      untagged_idx = self._mergeable[key]
                  except KeyError:
                      untagged_idx = len(self._untagged)
                      self._mergeable[key] = untagged_idx
                      self._untagged.append(resp)
                  else:
                      merged = self._untagged[untagged_idx].merge(resp)
                      self._untagged[untagged_idx] = merged
          self._raw = None
docs: Add an untagged response. These responses are shown before the
          parent response.
  
          Args:
              responses: The untagged responses to add.