mapSetGraphrefactor

size balanced b tree / avl
   code should be in one place.

in ghc 6.8.3, try gre -irl avl

Data.Graph.Inductive.Tree should use Data.Map, or perhaps should use something that Data.Map is also using.

Should then be easy to get serializeable instance for Gr.
  In HAppS.Data.Serialize there is already
-- note below, Data.Map doesn't export constructors.
instance Version (Map.Map a b) where mode = Primitive
instance (Serialize a,Serialize b, Eq a) => Serialize (Map.Map a b) where
    getCopy = contain ( fmap Map.fromAscList safeGet )
    putCopy m = contain . safePut . Map.toList $ m

We could then add 
-- note, Gr does export constructor Gr
instance Version (Gr a b) where mode = Primitive
instance (Serialize a,Serialize b, Eq a) => Serialize (Map.Map a b) where
    getCopy = contain ( fmap ( Gr . Map.fromAscList )safeGet )
    putCopy (Gr m) = contain . safePut . Map.toList $ m

 ??? no...

For now though the quicker fix is to simply add fromAscList to graph FiniteMap.