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