graph LR
subgraph outer
    subgraph inner
        A
    end
end
---
+-----------+
|   outer   |
|           |
|           |
| +-------+ |
| | inner | |
| |       | |
| |       | |
| | +---+ | |
| | |   | | |
| | | A | | |
| | |   | | |
| | +---+ | |
| |       | |
| +-------+ |
|           |
+-----------+