Bindings to Graphviz for graph visualisation. (http://projects.haskell.org/graphviz/)

#7Fails to display some edges

I'm converting from FGL. I want to get undirected graph, so I put edges in only one direction. However, if I add edge (X, Y, label) when X>Y, the edge does not appear in the resulting dot output.

graphInDot :: DotGraph Node
graphInDot = graphToDot nonClusteredParams{ isDirected = False
                                          , fmtNode = dotPrint
                                          , fmtEdge = \(_,_,el) -> [Label . StrLabel . T.pack . show $ el]
                                          }
                        exampleFoo

exampleFoo :: Gr String Int
exampleFoo = mkGraph [ ( 0, "stuff, things")
                     , ( 1, "stuff, things")
                     , ( 2, "stuff, things")
                     , ( 3, "stuff, things")
                     , ( 4, "stuff, things")
                     , ( 5, "stuff, things")
                     , ( 6, "stuff, things")
                     , ( 7, "stuff, things")
                     , ( 8, "stuff, things")
                     , ( 9, "stuff, things")
                     , (10, "stuff, things")
                     , (12, "stuff, things")
                     , (13, "stuff, things")
                     , (11, "stuff, things")
                     , (14, "stuff, things")
                     , (15, "stuff, things")
                     ]
                     $ map workaround
                           [ ( 1, 12,  0)
                           , ( 4, 12, 10)
                           , (12, 13, 11)
                           , ( 4,  5,  1)
                           , ( 5,  6,  2)
                           , ( 5,  8,  3)
                           , ( 8, 10,  4)
                           , ( 0,  7,  5)
                           , ( 2,  7,  6)
                           , ( 7,  9,  7)
                           , ( 9, 11,  8)
                           , ( 3,  9,  9)
                           , (15, 11, 12)         -- problem here
                           , (14, 11, 13)         -- problem here
                           ]