0(1) element: null
1(2) element: PyMatchStatement
2(3,10) refutable pattern: [] | 42
3(4,5) refutable pattern: []
4(8) matched pattern: []
5(6,10) refutable pattern: 42
6(7) matched pattern: 42
7(8) matched pattern: [] | 42
8(9) element: PyExpressionStatement
9(10) READ ACCESS: y
10(11) element: PyExpressionStatement
11(12) READ ACCESS: z
12() element: null