1921     type Item = I::Item;  typedef
1922     fn next(&mut self) -> Option<I::Item> {  in next()  argument
1928     fn nth(&mut self, n: usize) -> Option<I::Item> {  in nth()  argument
1931     fn last(self) -> Option<I::Item> {  in last()  argument
1937     type Item;  typedef
1938     fn last(self) -> Option<Self::Item>;  in last()  argument
1942     type Item = I::Item;  typedef
1943     default fn last(self) -> Option<I::Item> {  in last()  argument
1957     fn last(self) -> Option<I::Item> {  in last()  argument
1964     fn next_back(&mut self) -> Option<I::Item> {  in next_back()  argument
1967     fn nth_back(&mut self, n: usize) -> Option<I::Item> {  in nth_back()  argument
2016     fn from_iter<T: IntoIterator<Item = I>>(iter: T) -> Self {  in from_iter()  argument
2131     type Item = S::Item;  typedef
2133     fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {  in poll_next()  argument