Graph.incidentEdges

import std.algorithm : equal;

auto g1 = Graph!int([1, 2, 3]);

g1 ~= g1.edge(1, 1);
g1 ~= g1.edge(1, 2);
g1 ~= g1.edge(2, 2);
g1 ~= g1.edge(2, 3);

assert(g1.incidentEdges(1).equal([
    g1.edge(1, 1),
    g1.edge(1, 2),
]));
assert(g1.incidentEdges(2).equal([
    g1.edge(1, 2),
    g1.edge(2, 2),
    g1.edge(2, 3),
]));
assert(g1.incidentEdges(3).equal([
    g1.edge(2, 3),
]));