0(1) element: null
1(2) element: PyAssertStatement
2(3) READ ACCESS: isinstance
3(4) READ ACCESS: s
4(5) READ ACCESS: basestring
5(6) READ ACCESS: isinstance
6(7) READ ACCESS: x
7(8) READ ACCESS: int
8(9) ASSERTTYPE ACCESS: s
9(10) ASSERTTYPE ACCESS: x
10() element: null