Are there any gray cars or trains?
Yes, there is a gray train.
    src        edge_attr  dst
0     0  to the right of   10
1     0  to the right of   14
2     1  to the right of   18
3     1   to the left of    7
4     1  to the right of   16
..  ...              ...  ...
74   22   to the left of   18
75   23   to the left of    6
76   23  to the right of   17
77   23   to the left of    4
78   23   to the left of    5

[79 rows x 3 columns]