What makes up the cage, iron or wire?
The cage is made of iron.
    src        edge_attr  dst
0     0   to the left of    8
1     1   to the left of    8
2     4  to the right of   12
3     7  to the right of   14
4     7  to the right of   12
5     8  to the right of    0
6     8  to the right of    1
7     9  to the right of   12
8     9   to the left of   13
9    10   on the side of   12
10   12   to the left of    9
11   12   to the left of    4
12   12   to the left of    7
13   13  to the right of    9
14   14   to the left of    7