Remove unused sub-networks when generating multiple FAs.

src/GF/Speech/Graph.hs

@@ -18,6 +18,7 @@ module GF.Speech.Graph ( Graph(..), Node, Edge, NodeInfo
                         , nodeInfo
                         , getIncoming, getOutgoing, getNodeLabel
                         , inDegree, outDegree
+                        , nodeLabel
                         , edgeFrom, edgeTo, edgeLabel
                         , reverseGraph, renameNodes
                        ) where
@@ -149,6 +150,9 @@ groupEdgesBy f (Graph _ ns es) =
   where nm = Map.fromList [ (n, (x,[])) | (n,x) <- ns ]
 -}
 
+nodeLabel :: Node n a -> a
+nodeLabel = snd
+
 edgeFrom :: Edge n b -> n
 edgeFrom (f,_,_) = f