oncebu :: GenericM Maybe -> GenericM Maybe
oncebu f x = gmapMo (oncebu f) x `mplus` f x
oncebu :: GenericM Maybe -> GenericM Maybe
oncebu f x = gmapMo (oncebu f) x `mplus` f x
oncebu f x = gmapMo (oncebu f) x `mplus` f x