graph TD
subgraph one
    A --> B
end
---
+-------+
|  one  |
|       |
|       |
| +---+ |
| |   | |
| | A | |
| |   | |
| +---+ |
|   |   |
|   |   |
|   |   |
|   |   |
|   v   |
| +---+ |
| |   | |
| | B | |
| |   | |
| +---+ |
|       |
+-------+
