0(1) element: null
1(2) element: PyMatchStatement
2(3,12) refutable pattern: 1
3(4) matched pattern: 1
4(5) element: PyStatementList
5(6) element: PyMatchStatement
6(7,11) refutable pattern: 11
7(8) matched pattern: 11
8(9) element: PyStatementList
9(10) element: PyExpressionStatement
10(18) READ ACCESS: y11
11(18) ASSERTTYPE ACCESS: null
12(13,17) refutable pattern: 2
13(14) matched pattern: 2
14(15) element: PyStatementList
15(16) element: PyExpressionStatement
16(18) READ ACCESS: y2
17(18) ASSERTTYPE ACCESS: null
18(19) element: PyExpressionStatement
19(20) READ ACCESS: z
20() element: null