What is on the tray?
The cups are on the tray.
    src        edge_attr  dst
0     1   to the left of   11
1     1  to the right of    8
2     1  to the right of   21
3     1  to the right of   20
4     1   to the left of    4
..  ...              ...  ...
67   21        on top of   20
68   21               on   20
69   21        on top of    6
70   22               on    2
71   23  to the right of   16

[72 rows x 3 columns]