Are the gray bricks on the edge of the brick building?
Yes, the bricks are on the edge of the building.
    src        edge_attr  dst
0     0  to the right of    3
1     1               on    2
2     1  to the right of    3
3     1   on the side of    2
4     3   to the left of    0
5     3   to the left of    1
6     3  to the right of    4
7     3  to the right of    7
8     4   to the left of    3
9     5   on the edge of    2
10    6        on top of    2
11    7   to the left of    3
12    7               on    2
13    7               by    2