dgnPredName :: String -> LNode DGNodeLab -> Maybe (LNode DGNodeLab)
dgnPredName n nd@(_, lbl) = if getDGNodeName lbl == n then Just nd else Nothing
dgnPredName :: String -> LNode DGNodeLab -> Maybe (LNode DGNodeLab)
dgnPredName n nd@(_, lbl) = if getDGNodeName lbl == n then Just nd else Nothing
dgnPredName n nd@(_, lbl) = if getDGNodeName lbl == n then Just nd else Nothing