0(1) element: null
1(2) element: PyMatchStatement
2(3,13) refutable pattern: {"foo": 1, **x}
3(4,13) refutable pattern: "foo": 1
4(5,13) refutable pattern: "foo"
5(6) matched pattern: "foo"
6(7,13) refutable pattern: 1
7(8) matched pattern: 1
8(9) matched pattern: "foo": 1
9(10) WRITE ACCESS: x
10(11) matched pattern: {"foo": 1, **x}
11(12) element: PyExpressionStatement
12(13) READ ACCESS: y
13(14) element: PyExpressionStatement
14(15) READ ACCESS: z
15() element: null