Do the trees look leafless?
Yes, the trees are leafless.
    src        edge_attr  dst
0     2  to the right of    6
1     2  to the right of    4
2     3  to the right of    7
3     4   to the left of    2
4     4  to the right of    9
5     4   to the left of    6
6     6  to the right of    9
7     6   to the left of    2
8     6  to the right of    4
9     7   to the left of    3
10    9   to the left of    4
11    9   to the left of    6