Function second_transmission_zagreb 

pub fn second_transmission_zagreb(graph: &Graph) -> IgraphResult<u64>

Compute the second transmission Zagreb index.

TZ₂(G) = Σ_{(u,v)∈E} σ(u) · σ(v)

Self-loops are skipped.

Examples

use rust_igraph::{Graph, second_transmission_zagreb};

// Path 0-1-2: σ=[3,2,3]
// (0,1): 3×2=6, (1,2): 2×3=6 → TZ₂=12
let g = Graph::from_edges(&[(0,1),(1,2)], false, Some(3)).unwrap();
assert_eq!(second_transmission_zagreb(&g).unwrap(), 12);