Are there either cats or zebras?
No, there are no cats or zebras.
    src        edge_attr  dst
0     1   to the left of    2
1     1   to the left of    4
2     2  to the right of    9
3     2  to the right of    1
4     2   to the left of    4
5     2  to the right of   12
6     3   to the left of   10
7     4  to the right of    7
8     4  to the right of    8
9     4  to the right of   12
10    4  to the right of    6
11    4  to the right of    2
12    4  to the right of   14
13    4  to the right of   15
14    4  to the right of   13
15    4  to the right of    9
16    4  to the right of    1
17    5               of   11
18    6   to the left of    4
19    6   to the left of    7
20    7   to the left of    4
21    7  to the right of    6
22    8   to the left of    4
23    9   to the left of    2
24    9   to the left of    4
25   10  to the right of    3
26   12   to the left of    4
27   12   to the left of    2
28   13   to the left of    4
29   14   to the left of    4
30   15   to the left of    4