if the following are true:

• the line at time 23 = 2
• the tab at time 23 = 1
• statement at line 2, tab 1 = z = __add__(x, 3)
• expression state at time 23 = "end_expr"

then the tab at time 24 = 1

Start from the conclusion and work back up the proof. Click the arrow to show the parents.