What is the train made of?
The train is made of wood.
    src        edge_attr  dst
0     1   to the left of   19
1     2  to the right of    6
2     3   to the left of   13
3     4  to the right of   15
4     6   to the left of    9
..  ...              ...  ...
58   18   to the left of    7
59   18   to the left of   10
60   18   to the left of   13
61   18   to the left of    9
62   19  to the right of    1

[63 rows x 3 columns]