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: matrix_graph.rs
    path of file: ./repos/petgraph/src
    
    the code of the file until where you have to start completion: //! `MatrixGraph<N, E, Ty, NullN, NullE, Ix>` is a graph datastructure backed by an adjacency matrix.

use std::marker::PhantomData;
use std::ops::{Index, IndexMut};

use std::cmp;
use std::mem;

use indexmap::IndexSet;

use fixedbitset::FixedBitSet;

use crate::{Directed, Direction, Ed
    
    fn test_remove_node_and_edges_undirected() {
        let mut g = UnMatrix::new_undirected();
        let a = g.add_node('a');
        let b = g.add_node('b');
        let c = g.add_node('c');
        g.add_edge(a, b, ());
        g.add_edge(b, c, ());
        g.add_edge(c, a, ());

        // removing a should break the `a - b` and `a - c` edges
        g.remove_node(a);

        assert_eq!(g.node_count(), 2);

        let b_neighbors = g.neighbors(b).into_sorted_vec();
        assert_eq!(b_neighbors, vec![c]);

        let c_neighbors = g.neighbors(c).into_sorted_vec();
        assert_eq!(c_neighbors, vec![b]);
    }