You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: matching.rs
    path of file: ./repos/petgraph/src/algo
    
    the code of the file until where you have to start completion: use std::collections::VecDeque;
use std::hash::Hash;

use crate::visit::{
    EdgeRef, GraphBase, IntoEdges, IntoNeighbors, IntoNodeIdentifiers, NodeCount, NodeIndexab
    
    fn next(&mut self) -> Option<Self::Item> {
        while self.current != self.mate.len() {
            let current = self.current;
            self.current += 1;

            if let Some(mate) = self.mate[current] {
                // Check if the mate is a node after the current one. If not, then
                // do not report that edge since it has been already reported (the
                // graph is considered undirected).
                if self.graph.to_index(mate) > current {
                    let this = self.graph.from_index(current);
                    return Some((this, mate));
                }
            }
        }

        None
    }