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