"events with multiple entries (branch-joins and loop-heads):"
"events 2, 3, 10 are branch-joins."
"event 17 is a loop-head."
((2) (3) (10) (17))
"testing a depth-first traversal from root node:"
0
1
18
20
17
9
7
5
4
3
2
6
8
16
14
12
11
10
13
15
19
"showing loop-head-tail map:"
((17 . 2))
"showing loop-tail-head map:"
((2 . 17))
"there is only one loop"
"showing branch-head-tail pairs:"
((9 . 3) (16 . 10) (17 . 2))
"showing branch-tail-head pairs:"
((2 . 17) (3 . 9) (10 . 16))
"expect 3 pairs of branches, 2 of which are nested inside the third."
