What is the train pulling?
The train is pulling the train car.
     src        edge_attr  dst
0      0  to the right of   22
1      0   to the left of   21
2      0  to the right of   34
3      0   to the left of   32
4      1  to the right of    5
..   ...              ...  ...
186   34   to the left of   11
187   34   to the left of   21
188   34   to the left of   26
189   34   to the left of   13
190   34   to the left of   22

[191 rows x 3 columns]