The chain made of metal is what length?
The chain is long.
    src        edge_attr  dst
0     0  to the right of   12
1     1  to the right of    6
2     2   to the left of   11
3     2   to the left of    5
4     2  to the right of    9
5     2               on    7
6     5               by    8
7     5  to the right of    2
8     5  to the right of    6
9     6  to the right of   12
10    6   to the left of    1
11    6   to the left of   11
12    6   to the left of    5
13    9   to the left of    2
14   11  to the right of    6
15   11  to the right of    2
16   12               by    0
17   12   to the left of    6
18   12   to the left of    0
19   12   to the left of   13
20   13               on    8
21   13  to the right of   12