Who is facing left?
The zebras are facing left.
    src        edge_attr  dst
0     0               in   12
1     2   to the left of    6
2     2   to the left of    3
3     2   to the left of    7
4     2   to the left of    8
5     3               of    6
6     3  to the right of    2
7     4   to the left of    6
8     4               of    1
9     6  to the right of    2
10    6  to the right of    4
11    7               of    6
12    7  to the right of    2
13    8               of    6
14    8  to the right of    2
15    9               of    6
16   10               of    1