code: def _flat_values(self):
          
          return tuple(
              np.nan if type(x) is dict else x
              for x in self._cube_dict["result"]["measures"]["mean"]["data"]
          )
docs: Return tuple of mean values as found in cube response.
  
          Mean data may include missing items represented by a dict like
          {'?': -1} in the cube response. These are replaced by np.nan in the
          returned value.