createEdge :: Label -> Id -> Id -> GS Id
createEdge l snid enid = do (e, _, _) <- createEdgeRE l snid enid
                            return $ edgeId e
createEdge :: Label -> Id -> Id -> GS Id
createEdge l snid enid = do (e, _, _) <- createEdgeRE l snid enid
                            return $ edgeId e
createEdge l snid enid = do (e, _, _) <- createEdgeRE l snid enid
                            return $ edgeId e