Graph with no vertices
Tree:
directed: false
vcount: 0
edges: {
}
Vertex indices:


Graph with loops, multiple edges and isolated vertex:
Tree:
directed: true
vcount: 10
edges: {
0 1
0 2
1 3
2 7
2 8
3 4
3 9
6 1
}
Vertex indices:
0 1 2 3 4 5 1 0 3 4

Same graph, undirected:
Tree:
directed: false
vcount: 10
edges: {
0 1
0 2
0 6
1 3
1 7
2 8
3 4
3 9
}
Vertex indices:
0 1 2 3 4 5 2 1 3 4

Almost same graph, two roots:
Tree:
directed: true
vcount: 12
edges: {
0 1
0 2
1 3
2 7
2 8
3 4
3 9
6 1
10 5
11 5
}
Vertex indices:
0 1 2 3 4 5 1 0 3 4 5 5

Same graph, multiple roots in same tree:
Tree:
directed: true
vcount: 10
edges: {
0 1
0 2
1 3
2 7
2 8
3 4
3 9
6 1
}
Vertex indices:
0 1 2 3 4 5 1 0 3 4

Check error for root out of bounds.
