{"ast_node_type":"function","tokens":[{"end":72,"kind":"keyword","start":0,"text":"fn"}]}
    fn extend<I: IntoIterator<Item = (Idx<V>, T)>>(&mut self, iter: I) {
impl<T, V> Extend<(Idx<V>, T)> for ArenaMap<Idx<V>, T> {
        iter.into_iter().for_each(move |(k, v)| {