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