Null graph
directed: false
vcount: 0
edges: {
}

Directed null graph
directed: true
vcount: 0
edges: {
}

Singleton graph
directed: false
vcount: 1
edges: {
}

Path graph
directed: true
vcount: 3
edges: {
0 1
1 2
}

Binary out-tree, n=3
directed: true
vcount: 3
edges: {
0 1
0 2
}

Binary in-tree, n=3
directed: true
vcount: 3
edges: {
1 0
2 0
}

Ternary out-tree, n=14
directed: true
vcount: 14
edges: {
0 1
0 2
0 3
1 4
1 5
1 6
2 7
2 8
2 9
3 10
3 11
3 12
4 13
}