Feature request: more transparency for Data.Graph.Inductive.NodeMap

[Misha Aizatulin]

hello,

   would it be possible to add functions to NodeMap for inspecting the 
contents of the map? I would be particularly interested in a function like
   toList :: NodeMap a -> [LNode a]

   If I use a node map m to construct a graph g, then of course 
(labNodes g) would achieve the same as (toList m), but if I later 
transform the labels of the graph, say using nmap, then I cannot do it 
anymore - the connection between old label values and nodes is still a 
valuable piece of information, but I cannot access it.

Cheers,
   Misha