0(1) element: null
1(2) element: PyMatchStatement
2(3) refutable pattern: [] | 42
3(4,5) refutable pattern: []
4(7) matched pattern: []
5(6,11) refutable pattern: 42
6(7) matched pattern: 42
7(8) matched pattern: [] | 42
8(9) element: PyStatementList
9(10) element: PyExpressionStatement
10(12) READ ACCESS: y
11(12) ASSERTTYPE ACCESS: null
12(13) element: PyExpressionStatement
13(14) READ ACCESS: z
14() element: null