> pss("square_tiling", "1122", nrow = 7, ncol = 9)
/ - - - - - - - - - \ 
| 2 2 2 2 2 2 2 2 2 | 
| 1 1 1 1 1 1 1 1 1 | 
| 2 2 2 2 2 2 2 2 2 | 
| 1 1 1 1 1 1 1 1 1 | 
| 2 2 2 2 2 2 2 2 2 | 
| 1 1 1 1 1 1 1 1 1 | 
| 2 2 2 2 2 2 2 2 2 | 
\ - - - - - - - - - / 

