modifyEdge :: (Edge -> Edge) -> EdgeId -> StGNG a ()
modifyEdge f eid = State.modify (&edges %~ Map.adjust f eid)
modifyEdge :: (Edge -> Edge) -> EdgeId -> StGNG a ()
modifyEdge f eid = State.modify (&edges %~ Map.adjust f eid)
modifyEdge f eid = State.modify (&edges %~ Map.adjust f eid)