Function bellman_ford_single_source 

pub fn bellman_ford_single_source<T, S>(
    graph: &S,
    source: usize,
    directed: bool,
    returnpredecessors: bool,
) -> SparseResult<(Array1<T>, Option<Array1<isize>>)>
where
    T: Float + Debug + Copy + 'static,
    S: SparseArray<T>,

Bellman-Ford algorithm for single source shortest paths