pub type ComputeFrom2<I, T, S1I, S1T, S2I, S2T> = for<'a> fn(I, &mut dyn BaseVecIterator<Item = (S1I, Cow<'a, S1T>)>, &mut dyn BaseVecIterator<Item = (S2I, Cow<'a, S2T>)>) -> Option<T>;pub type ComputeFrom2<I, T, S1I, S1T, S2I, S2T> = for<'a> fn(I, &mut dyn BaseVecIterator<Item = (S1I, Cow<'a, S1T>)>, &mut dyn BaseVecIterator<Item = (S2I, Cow<'a, S2T>)>) -> Option<T>;