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(12) READ ACCESS: y
7(8,11) WRITE ACCESS: x
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