313         self.call_cindex(py, "deltachain", args, kw)

   313         let index = self.index(py).borrow();

   314         let rev = args.get_item(py, 0).extract::<BaseRevision>(py)?.into();

   315         let stop_rev =

   316             args.get_item(py, 1).extract::<Option<BaseRevision>>(py)?;

   317         let rev = index.check_revision(rev).ok_or_else(|| {

   318             nodemap_error(py, NodeMapError::RevisionNotInIndex(rev))

   319         })?;

   320         let stop_rev = if let Some(stop_rev) = stop_rev {

   321             let stop_rev = UncheckedRevision(stop_rev);

   322             Some(index.check_revision(stop_rev).ok_or_else(|| {

   323                 nodemap_error(py, NodeMapError::RevisionNotInIndex(stop_rev))

   324             })?)

   325         } else {None};

   326         let (chain, stopped) = index.delta_chain(rev, stop_rev).map_err(|e| {

   327             PyErr::new::<cpython::exc::ValueError, _>(py, e.to_string())

   328         })?;

   329 

   330         let cresult = self.call_cindex(py, "deltachain", args, kw)?;

   331         let cchain: Vec<BaseRevision> =

   332             cresult.get_item(py, 0)?.extract::<Vec<BaseRevision>>(py)?;

   333         let chain: Vec<_> = chain.into_iter().map(|r| r.0).collect();

   334         assert_eq!(chain, cchain);

   335         assert_eq!(stopped, cresult.get_item(py, 1)?.extract(py)?);

   336 

   337         Ok(

   338             PyTuple::new(

   339                 py,

   340                 &[

   341                     chain.into_py_object(py).into_object(),

   342                     stopped.into_py_object(py).into_object()

   343                 ]

   344             ).into_object()

   345         )

   346