E.g.:

```rust
// just an example, can be any Iterator<Item = char>
let iter = "hello".chars();

let mut path = std::path::PathBuf::new();

// works but is inefficient
path.push(iter.collect::<String>());

// does not work:
//   path.push(iter);
// if path were String we could do
//   path.extend(iter)
println!("{:?}", path);

```