Function graph_periphery 

pub fn graph_periphery(
    graph: &Graph,
    mode: EccMode,
) -> IgraphResult<Vec<VertexId>>

Return the periphery vertices of a graph.

A vertex belongs to the periphery if its eccentricity equals the graph diameter (maximum eccentricity). For directed graphs, mode controls BFS direction.

Returns an empty vector for an empty graph.

Examples

use rust_igraph::{Graph, graph_periphery, EccMode};

// Path 0-1-2-3-4: periphery is {0, 4} (eccentricity 4 = diameter)
let g = Graph::from_edges(&[(0,1),(1,2),(2,3),(3,4)], false, Some(5)).unwrap();
let peri = graph_periphery(&g, EccMode::All).unwrap();
assert_eq!(peri, vec![0, 4]);