@sig(H[(Traversable, "t")]/ (H/ "a" >> "b" >> ("a", "c")) >> "a" >> t("t", "b")
        >> ("a", t("t", "c")))
def mapAccumR(f, a, tb):
    raise NotImplementedError()
mapAccumR :: Traversable t => (a -> b -> (a, c)) -> a -> t b -> (a, t c)
dataset/ETHPy150Open billpmurphy/hask/hask/Data/Traversable.py/mapAccumR