0(1) element: null
1(2) element: PyMatchStatement
2(3,12) refutable pattern: [1 | x]
3(4) refutable pattern: 1 | x
4(5,6) refutable pattern: 1
5(7) matched pattern: 1
6(7,12) WRITE ACCESS: x
7(8) matched pattern: 1 | x
8(9) matched pattern: [1 | x]
9(10) element: PyStatementList
10(11) element: PyExpressionStatement
11(13) READ ACCESS: y
12(13) ASSERTTYPE ACCESS: null
13(14) element: PyExpressionStatement
14(15) READ ACCESS: z
15() element: null