.shape().begin());     if(opt.to_point != Shape())         tmpShape = opt.to_point-opt.from_point;          res.reshapeIfEmpty(volume.taggedShape().resize(tmpShape).setChannelDescription(description),               "gaussianGradientMagnitude(): Output array has wrong shape.");          {         PyAllowThreads _pythread;         MultiArray<sdim, TinyVector<VoxelType, sdim> > grad(tmpShape);                  for(int k=0; k<