pub fn random_lts(num_of_states: usize, num_of_labels: u32, outdegree: usize) -> LabelledTransitionSystem {

    // Introduce lower case letters for the labels.

    let tau_label = "tau".to_string();

    let mut labels: Vec<String> = vec![tau_label.clone()];

    for i in 0..num_of_labels {

        labels.push(char::from_digit(i + 10, 36).unwrap().to_string());

    }

    let mut rng = rand::rng();

    let mut transitions: FxHashSet<(usize, usize, usize)> = FxHashSet::default();

    for state_index in 0..num_of_states {

        for _ in 0..rng.random_range(0..outdegree) {

            // Pick a random label and state.

            let label = rng.random_range(0..num_of_labels);

            let to = rng.random_range(0..num_of_states);

            transitions.insert((state_index, label as usize, to));

        }

    LabelledTransitionSystem::new(0, 

        Some(num_of_states),

        || transitions.iter().cloned(),

        labels, 

        vec![tau_label])

}

    #[test]