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