What type of vehicle is to the left of the person that is wearing a cap?
The vehicle is a truck.
    src        edge_attr  dst
0     0          wearing   15
1     0   to the left of   13
2     0          wearing    5
3     0  to the right of   18
4     0  to the right of    9
5     0   walking across    1
6     1  to the right of   18
7     2  to the right of   14
8     3   to the left of    6
9     3          wearing   11
10    3   to the left of    8
11    5  to the right of    9
12    5   to the left of   13
13    6  to the right of   17
14    6  to the right of    3
15    7  to the right of    9
16    7            below   19
17    8  to the right of    3
18    8  to the right of   17
19    9   to the left of   15
20    9   to the left of   13
21    9   to the left of    0
22    9   to the left of    5
23    9   to the left of    7
24   10   to the left of   16
25   13  to the right of    9
26   13  to the right of    5
27   13  to the right of    0
28   13  to the right of   18
29   14   to the left of   16
30   14   to the left of    2
31   15  to the right of    9
32   16  to the right of   14
33   16  to the right of   10
34   17   to the left of    6
35   17   to the left of    8
36   18   to the left of   13
37   18   to the left of    0
38   18   to the left of    1
39   19            above    7