No vertices:
directed: false
vcount: 0
edges: {
}
No edges:
directed: false
vcount: 5
edges: {
}
A star with double edges.
directed: true
vcount: 10
edges: {
1 0
1 0
2 0
2 0
3 0
3 0
4 0
4 0
5 0
5 0
6 0
6 0
7 0
7 0
8 0
8 0
9 0
9 0
}