pub trait TokenSlice<'a, T> {
// Required method
fn get_args_into(&'a self, args: &mut HashMap<&'a T, HashSet<ArgType>>)
where T: Deref<Target = str> + Clone;
// Provided method
fn get_args(&'a self) -> HashMap<&'a T, HashSet<ArgType>>
where T: Deref<Target = str> + Clone { ... }
}