newTrans :: Monad m => [PlaceNo] -> [PlaceNo] -> [PNExpr] ->
        MkPNMonad m value TransNo
    newTrans inPlaces outPlaces exprs = do
        label <- getLabel
        addTrans $ Trans label inPlaces outPlaces Nothing exprs $ const $ return ()
newTrans :: Monad m => [PlaceNo] -> [PlaceNo] -> [PNExpr] ->
        MkPNMonad m value TransNo
newTrans inPlaces outPlaces exprs = do
        label <- getLabel
        addTrans $ Trans label inPlaces outPlaces Nothing exprs $ const $ return ()
newTrans inPlaces outPlaces exprs = do
        label <- getLabel
        addTrans $ Trans label inPlaces outPlaces Nothing exprs $ const $ return ()