Fix return description of private func

Author: bobleesj

diffpy/snmf/containers.py

@@ -36,7 +36,7 @@ def _interpolate_stretching_factor(self, stretching_factor):
         Returns
         -------
         NDArray[float64]
-            The interpolated values over the stretched grid.
+          Interpolated values of the self.iq values over the grid that has been adjusted by the stretching_factor
         """
 
         normalized_grid = np.arange(len(self.grid))