withLabel :: String -> MkPNMonad SimFlow SimValue a -> MkPNMonad SimFlow SimValue a
    withLabel label m = do
        pushLabel label
        ret <- m
        popLabel
        return ret
withLabel :: String -> MkPNMonad SimFlow SimValue a -> MkPNMonad SimFlow SimValue a
withLabel label m = do
        pushLabel label
        ret <- m
        popLabel
        return ret
withLabel label m = do
        pushLabel label
        ret <- m
        popLabel
        return ret