+import Types.Data.Bool
+
+-- Graph is a map from node ID to context
+data Context preNodes node sucNodes
+data Graph nodeMap
+
+-- Empty
+type Empty = Graph Nil
+
+-- IsEmpty
+type family IsEmpty g
+type instance IsEmpty (Graph Nil) = True
+type instance IsEmpty (Graph (Cons x xs)) = False
+
+-- Match
+--type Match n g
+-- =