Which color is the controller in the middle?
The controller is white.
    src        edge_attr  dst
0     1   to the left of   14
1     2   to the left of    3
2     2   to the left of   14
3     3  to the right of   11
4     3  to the right of   19
5     3  to the right of   17
6     3  to the right of    2
7     4   to the left of   16
8     4           behind   16
9     4   to the left of   14
10    4   to the left of    8
11    5   to the left of    8
12    5               of   14
13    6               of   14
14    6  to the right of   17
15    6  to the right of   11
16    6  to the right of   19
17    7               of   14
18    7   to the left of    8
19    8               of   14
20    8  to the right of   16
21    8   to the left of   18
22    8  to the right of    5
23    8  to the right of    4
24    8  to the right of   12
25    8  to the right of    7
26   10   to the left of   14
27   10               on   15
28   11               of   17
29   11   to the left of    3
30   11   to the left of    6
31   12   to the left of    8
32   13  to the right of   15
33   14          holding   19
34   14  to the right of    1
35   14  to the right of    4
36   14  to the right of    2
37   14  to the right of   10
38   15   to the left of   13
39   16            above   17
40   16   to the left of    8
41   16  to the right of    4
42   16      in front of    4
43   17   to the left of    6
44   17               on   15
45   17   to the left of    3
46   17            below   16
47   18               of   14
48   18  to the right of    8
49   19   to the left of    3
50   19   to the left of    6