Function backtrack_edges 

pub fn backtrack_edges<K, N, E>(
    edges: &Vec<Weak<Edge<K, N, E>>>,
) -> Vec<Weak<Edge<K, N, E>>>
where
    K: Hash + Eq + Clone + Debug + Display + Sync + Send,
    N: Clone + Debug + Display + Sync + Send,
    E: Clone + Debug + Display + Sync + Send,

Backtrack edges in an edge list starting from the last edge in the list. Used for example to find the shortest path from the results of a breadth first straversal.