pub(crate) trait UniqueIndexExt: Iterator<Item = usize> {
    // Provided method
    fn unique<'a>(
        self,
        scratch: &'a mut UniqueIndexScratch,
    ) -> UniqueIndex<'a, Self> ⓘ
       where Self: Sized { ... }
}pub(crate) trait UniqueIndexExt: Iterator<Item = usize> {
    // Provided method
    fn unique<'a>(
        self,
        scratch: &'a mut UniqueIndexScratch,
    ) -> UniqueIndex<'a, Self> ⓘ
       where Self: Sized { ... }
}