Function network_simplex 

pub fn network_simplex<G, F, Bs, Ls, Us, Cs>(
    g: &G,
    balances: Bs,
    lower: Ls,
    upper: Us,
    costs: Cs,
) -> Option<(F, Vec<(G::Edge<'_>, F)>)>
where
    G: IndexDigraph,
    F: NumAssign + NumCast + FromPrimitive + Ord + Signed + Bounded + Copy,
    Bs: Fn(G::Node<'_>) -> F,
    Ls: Fn(G::Edge<'_>) -> F,
    Us: Fn(G::Edge<'_>) -> F,
    Cs: Fn(G::Edge<'_>) -> F,

Solve a min-cost-flow problem with a network simplex algorithm.

The function returns the objective value and the optimal flow.