What is located on top of the tray?
The cellphones are on top of the tray.
    src        edge_attr  dst
0     0  to the right of   17
1     0   to the left of    6
2     0   to the left of   21
3     0  to the right of   20
4     1   to the left of    6
..  ...              ...  ...
84   26   to the left of   16
85   26   to the left of   13
86   27   to the left of   26
87   27   to the left of    2
88   27   to the left of   16

[89 rows x 3 columns]