fix issue 6840 format

Signed-off-by: Wei_Chuan, Chiang <[email protected]>

Author: slicepaste

monai/data/meta_tensor.py

@@ -479,7 +479,7 @@ def pixdim(self):
 
     def set_pixdim(self) -> None:
         """Update pixdim based on current affine."""
-        self.meta[MetaKeys.PIXDIM][1:1+len(self.pixdim)] = affine_to_spacing(self.affine)
+        self.meta[MetaKeys.PIXDIM][1 : 1 + len(self.pixdim)] = affine_to_spacing(self.affine)
 
     def peek_pending_shape(self):
         """