pub trait Store<N, V>: Extend<Edge<N, V>> + IndexMut<N, Output = Vec<(N, V), Global>>where
N: Node,{
// Required methods
fn clear(&mut self);
fn contains_key(&self, key: &N) -> bool;
fn drain(&mut self);
fn entry(&mut self, key: N);
// Provided method
fn get(&self, key: &N) -> Option<&Vec<(N, V), Global>> { ... }
}