What kind of watercraft are the mountains behind of?
The mountains are behind the boats.
    src    edge_attr  dst
0     0        below    3
1     1        below    3
2     2       behind    3
3     2         near    3
4     2  in front of    5
5     3           on    1
6     3         near    2
7     3  in front of    2
8     5       behind    6
9     5       behind    2
10    6           in    2
11    6  in front of    5