1 files changed, 9 insertions, 0 deletions
diff --git a/chain/src/item/default/mod.rs b/chain/src/item/default/mod.rs
index 01e463e..f532805 100644
--- a/chain/src/item/default/mod.rs
+++ b/chain/src/item/default/mod.rs
@@ -127,6 +127,11 @@ impl<T: GraphLabel> LabelGraph<T> for DefaultForest<T> {
     where
         Self: 'a;
 
+    type TupleIter<'a> = std::iter::Empty<(T, usize)>
+    where
+        Self: 'a,
+        T: 'a;
+
     type LabelIter<'a> = std::iter::Empty<(&'a T, <Self as LabelGraph<T>>::Iter<'a>)>
     where
         Self: 'a,
@@ -163,6 +168,10 @@ impl<T: GraphLabel> LabelGraph<T> for DefaultForest<T> {
         unimplemented!("edges have no labels")
     }
 
+    fn tuples_of(&self, _node_id: usize) -> Result<Self::TupleIter<'_>, GError> {
+        unimplemented!("edges have no labels")
+    }
+
     fn labels_of(&self, _node_id: usize) -> Result<Self::LabelIter<'_>, GError> {
         unimplemented!("edges have no labels")
     }