fix bug

majosm · majosm · commit 12a64438282e · 2022-08-09T16:12:53.000-05:00
diff --git a/grudge/trace_pair.py b/grudge/trace_pair.py
@@ -918,7 +918,7 @@ def cross_rank_inter_volume_trace_pairs(
     # }}}
 
     if dcoll.mpi_communicator is None:
-        return []
+        return {}
 
     rank = dcoll.mpi_communicator.Get_rank()
 
