Function first_transmission_zagreb 

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

Compute the first transmission Zagreb index.

TZ₁(G) = Σ_v σ(v)² where σ(v) = Σ_w d(v,w).

Examples

use rust_igraph::{Graph, first_transmission_zagreb};

// Path 0-1-2: σ(0)=3, σ(1)=2, σ(2)=3
// TZ₁ = 9 + 4 + 9 = 22
let g = Graph::from_edges(&[(0,1),(1,2)], false, Some(3)).unwrap();
assert_eq!(first_transmission_zagreb(&g).unwrap(), 22);