docs: def _get_result(self, idx, timeout=None):
          """Called by the CollectorIterator object to retrieve the
          result's values one after another (order defined by the
          implementation)
          \param idx The index of the result we want, wrt collector's order
          \param timeout integer telling how long to wait (in seconds)
          for the result at index idx to be available, or None (wait
          forever)
          """
          res = self._results[idx]
          res.wait(timeout)
          return res