Change GraphTopologyConversion::convert return value to include the new GraphIsomorphism

This allows to convert maps for the converted graph.

src/lib.rs

@@ -146,8 +146,8 @@ pub mod traits;
 /// Convenience re-exports of graph topology traits for common use.
 pub mod prelude {
     pub use crate::traits::{
-        GraphTopology, GraphTopologyAddition, GraphTopologyConversion, GraphTopologyDeletion,
-        Incidence, IncidenceCursor,
+        GraphIsomorphism, GraphTopology, GraphTopologyAddition, GraphTopologyConversion,
+        GraphTopologyDeletion, Incidence, IncidenceCursor,
     };
 }