0(1) element: null
1(2) element: PyIfStatement
2(3) READ ACCESS: xs
3(4,6) READ ACCESS: None
4(5) element: null. Condition: xs is None:false
5(11) ASSERTTYPE ACCESS: xs
6(7) element: null. Condition: xs is None:true
7(8) ASSERTTYPE ACCESS: xs
8(9) element: PyStatementList
9(10) element: PyAssignmentStatement
10(11) WRITE ACCESS: xs
11(12) element: PyPrintStatement
12(13) READ ACCESS: xs
13() element: null